Biomedical subjects

B Müller

Publications and source records attributed to B Müller.

At least 109 records · Page 6Linked to original sources

PubMed2001

Multipotential nestin-positive stem cells isolated from adult pancreatic islets differentiate ex vivo into pancreatic endocrine, exocrine, and hepatic phenotypes.

The endocrine cells of the rat pancreatic islets of Langerhans, including insulin-producing beta-cells, turn over every 40-50 days by processes of apoptosis and the proliferation and differentiation of new islet cells (neogenesis) from progenitor epithelial cells located in the pancreatic ducts. However, the administration to rats of islet trophic factors such as glucose or glucagon-like peptide 1 for 48 h results in a doubling of islet cell mass, suggesting that islet progenitor cells may reside within the islets themselves. Here we show that rat and human pancreatic islets contain a heretofore unrecognized distinct population of cells that express the neural stem cell-specific marker nestin. Nestin-positive cells within pancreatic islets express neither the hormones insulin, glucagon, somatostatin, or pancreatic polypeptide nor the markers of vascular endothelium or neurons, such as collagen IV and galanin. Focal regions of nestin-positive cells are also identified in large, small, and centrolobular ducts of the rat pancreas. Nestin-positive cells in the islets and in pancreatic ducts are distinct from ductal epithelium because they do not express the ductal marker cytokeratin 19 (CK19). After their isolation, these nestin-positive cells have an unusually extended proliferative capacity when cultured in vitro (approximately 8 months), can be cloned repeatedly, and appear to be multipotential. Upon confluence, they are able to differentiate into cells that express liver and exocrine pancreas markers, such as alpha-fetoprotein and pancreatic amylase, and display a ductal/endocrine phenotype with expression of CK19, neural-specific cell adhesion molecule, insulin, glucagon, and the pancreas/duodenum specific homeodomain transcription factor, IDX-1. We propose that these nestin-positive islet-derived progenitor (NIP) cells are a distinct population of cells that reside within pancreatic islets and may participate in the neogenesis of islet endocrine cells. The NIP cells that also reside in the pancreatic ducts may be contributors to the established location of islet progenitor cells. The identification of NIP cells within the pancreatic islets themselves suggest possibilities for treatment of diabetes, whereby NIP cells isolated from pancreas biopsies could be expanded ex vivo and transplanted into the donor/recipient.

Animals↗

PubMed2001

Induction of soluble antitumoral mediators by synthetic analogues of bacterial lipoprotein in bone marrow-derived macrophages from LPS-responder and -nonresponder mice.

Macrophage-dependent antitumoral activity is partly mediated by soluble factors including cytokines, reactive-oxygen intermediates (ROIs), and reactive-nitrogen intermediates (RNIs). Activation of macrophages for tumor cytotoxicity can be achieved with various bacterial compounds, such as lipopolysaccharides (LPSs), muramyl-dipeptides, and lipopeptides. We studied the production and release of oxygen radicals, nitric oxide, and tumor necrosis factor alpha (TNF-alpha) by bone marrow-derived macrophages (BMDMs) of different mouse inbred strains after they were stimulated with the lipopeptide P3CSK4, a water-soluble synthetic analogue of the lipidated N terminus of bacterial lipoprotein. The lipopeptide was able to induce a strong, long lasting release of oxygen radicals in BALB/c mouse macrophages. Furthermore, it induced nitric oxide release from BMDMs of several mouse strains (BALB/c, C57Bl/6, C57Bl/10ScSn, Sv129, NMRI, and LPS-nonresponder C57Bl/10ScCr). Stimulation with P3CSK4 also resulted in comparable production of TNF-alpha in LPS-responder and nonresponder BMDMs from C57Bl/10ScSn mice and C57Bl/10ScCr mice, respectively. All three antitumoral mediators reached functional levels or concentrations as shown by the strong cytostatic/cytotoxic activity of lipopeptide-activated macrophages for the cell lines Abelson 8-1, M12.5/P815, and L929, which are sensitive to ROIs, nitric oxide, and TNF-alpha, respectively. We found that synthetic lipopeptides can induce the secretion of effective levels of soluble tumor-cytotoxic/cytostatic mediators in BMDMs of LPS-responsive and, of particular interest, also of LPS-unresponsive mice. This result could indicate that the highly effective bacterial-macrophage activators P3CSK4 and LPS use different receptors and/or different intracellular signal transduction pathways.

Acridines↗

PubMed2001

Prospective 10-year follow-up in adolescent anorexia nervosa--course, outcome, psychiatric comorbidity, and psychosocial adaptation.

The aim of the present study was to follow up the long-term course of adolescent-onset anorexia nervosa by repeated assessment, to analyze the association between the course of the eating disorder and psychiatric comorbidity, and to evaluate psychosocial outcome. The sample consisted of 39 inpatients who were reinvestigated 3, 7, and 10 years after discharge. The patients and 39 controls matched for age, gender, and occupational status were assessed with structured interviews on DSM-III-R eating disorders, additional axis I and axis II psychiatric disorders, and psychosocial functioning. Results showed that 69 % of the original subjects met the criteria for full recovery at the 10-year follow-up. One patient (3%) still exhibited the full syndrome of restrictive anorexia nervosa, two patients (5%) the full syndrome of bulimia nervosa. None of the patients had died. Of the subjects, 51% currently had an axis I psychiatric disorder and 23% met the full criteria for a personality disorder. Apart from the eating disorder, anxiety disorders and avoidant-dependent and obsessive-compulsive personality disorders were the most common psychiatric diagnoses. There was a significant association between psychiatric comorbidity and the outcome of the eating disorder and between outcome and psychosocial adaptation. With regard to psychiatric morbidity and psychosocial functioning, long-term recovered patients did not differ significantly from normal controls. It is concluded that in most patients adolescent anorexia nervosa takes a prolonged course, although it seems to be more favorable than in adult-onset forms. Those who achieve complete recovery from the eating disorder have a good chance of overcoming other psychiatric disorders and to adapt to social requirements.

Adaptation, Psychological↗

PubMed2001

DNA short tandem repeat profiling of three North Indian populations.

POPULATION: Fifty healthy unrelated individuals were randomly chosen from each of the three populations viz., Bhargavas, Chaturvedies, and Brahmins. Three generation pedigree charts were prepared to ensure sirname endogamy in Bhargavas Chaturvedies and group endogamy in Brahmins subjects were chosen from several parts of Uttar Pradesh, a northern state of the Indian republic.

Alleles↗

PubMed2000

[Suicidality in the elderly. What to do when the patient is suicidal?].

The suicide rate shows a constant increase with age, and the reasons are multifactorial. In particular people with mental disturbances, especially depression, age-related multimorbidity and loneliness, have a tendency towards suicidal behavior. Therapeutic approaches are grounded in the early recognition of direct and indirect remarks indicative of suicidal tendencies, and in binding agreements on necessary therapeutic measures. For the future, there is an urgent need for further expansion of the cooperative effort between physicians and care-providing and social services in multiprofessional teams that also involve relatives, together with training in crisis intervention in suicidal persons.

Aged↗

PubMed2000

Screening for high-grade cervical intra-epithelial neoplasia and cancer by testing for high-risk HPV, routine cytology or colposcopy.

The validity of testing for high-risk types of human papillomavirus (HPV) in cervical cancer prevention programs is undetermined. We compared the performance on primary screening of HPV DNA testing, cytology and colposcopy in detecting cervical intra-epithelial neoplasia (CIN) grade 2 or 3 or cancer. A cohort of 4,761 women, median age 35 years, was screened by routine cytology, routine colposcopy and testing for high-risk HPV by a PCR-based method. Within an 8-month period, women with abnormal findings on cytology or screening colposcopy or in whom high-risk HPV types were detected were referred for colposcopy and biopsy. Women negative on all initial screening tests were followed by a second screening examination. To correct for work-up bias, the true prevalence of CIN 2 or 3 or cancer was estimated by projection from histologically verified subgroups. Cervical biopsies were taken in 364 women (7.6%), of whom 114 (2.4%) showed CIN 2 (n = 34) or CIN 3 (n = 71) or cancer (n = 9). High-risk HPV testing achieved bias-corrected performance measures of 89.4% sensitivity, 93.9% specificity, 35.8% positive predictive value and 99.6% negative predictive value. Bias-corrected rates of true- and false-positives by high-risk HPV testing compared to cytology (colposcopy) were about 4.5 (6.7) and 19.1 (7.4) times higher, respectively. The quality of routine cytology was controlled by computer-assisted review, and the observed number of true-positives more than doubled after adding automated review results. In middle-aged women, testing for high-risk HPV types, particularly when negative, may be used to increase the screening interval in programs for secondary prevention of cervical cancer.

Adult↗

PubMed2000

Direct transcriptional control of the Dpp target omb by the DNA binding protein Brinker.

The gradient morphogen Decapentaplegic (Dpp) organizes pattern by inducing the transcription of different target genes at distinct threshold concentrations during Drosophila development. An important, albeit indirect, mode by which Dpp controls the spatial extent of its targets is via the graded downregulation of brinker, whose product in turn negatively regulates the expression of these targets. Here we report the molecular dissection of the cis-regulatory sequences of optomotor-blind (omb), a Dpp target gene in the wing. We identify a minimal 284 bp Dpp response element and demonstrate that it is subject to Brinker (Brk) repression. Using this omb wing enhancer, we show that Brk is a sequence-specific DNA binding protein. Mutations in the high-affinity Brk binding site abolish responsiveness of this omb enhancer to Brk and also compromise the input of an unknown transcriptional activator. Our results therefore identify Brk as a novel transcription factor antagonizing Dpp signalling by directly binding target genes and repressing their expression.

Animals↗

PubMed2000

Assembly of U7 small nuclear ribonucleoprotein particle and histone RNA 3' processing in Xenopus egg extracts.

In animals, replication-dependent histone genes are expressed in dividing somatic cells during S phase to maintain chromatin condensation. Histone mRNA 3'-end formation is an essential regulatory step producing an mRNA with a hairpin structure at the 3'-end. This requires the interaction of the U7 small nuclear ribonucleoprotein particle (snRNP) with a purine-rich spacer element and of the hairpin-binding protein with the hairpin element, respectively, in the 3'-untranslated region of histone RNA. Here, we demonstrate that bona fide histone RNA 3' processing takes place in Xenopus egg extracts in a reaction dependent on the addition of synthetic U7 RNA that is assembled into a ribonucleoprotein particle by protein components available in the extract. In addition to reconstituted U7 snRNP, Xenopus hairpin-binding protein SLBP1 is necessary for efficient processing. Histone RNA 3' processing is not affected by addition of non-destructible cyclin B, which drives the egg extract into M phase, but SLBP1 is phosphorylated in this extract. SPH-1, the Xenopus homologue of human p80-coilin found in coiled bodies, is associated with U7 snRNPs. However, this does not depend on the U7 RNA being able to process histone RNA and also occurs with U1 snRNPs; therefore, association of SPH1 cannot be considered as a hallmark of a functional U7 snRNP.

3' Untranslated Regions↗

PubMed2000

MRI of small human stroke shows reversible diffusion changes in subcortical gray matter.

Six patients who had suffered small cerebral ischemia affecting subcortical gray matter were examined with diffusion weighted imaging (DWI) and T2-weighted imaging within the first 8 h, during the next 2 days and after 5-16 days. Areas of apparent diffusion coefficient (ADC) decreases were observed acutely and reached the maximum size during the subsequent 2 days. Noticeably, in all subjects, a large portion of the ADC lesion was reversible as judged from the lesion size on final T2 image. The regular reversibility of the ADC decreases in this setting may indicate a hitherto not understood pathophysiological process occurring in small ischemic stroke.

Adult↗

PubMed2000

Serotonergic platelet variables in unmedicated patients suffering from major depression and healthy subjects: relationship between 5HT content and 5HT uptake.

The dependence of platelet-5HT content on apparent kinetic parameters of 5HT uptake was analyzed in 56 healthy subjects and 47 depressed patients, who had not been taking psychotropic medication for several months. There were no significant relationships between apparent Vmax or Km and platelet-5HT content in both groups. However, the ratio of Vmax to Km, as a measure of apparent 5HT uptake efficiency, significantly correlated with the platelet-5HT concentration in healthy subjects (r=0.627 p<0.001). Female controls showed a higher correlation coefficient (r=0.723) than male controls (r=0.457). A marked deviation from the linear relationship between 5HT content and the ratio Vmax/K was observed in female depressed patients (r=0.250 n.s.). In male depressed patients the correlation coefficient (r=0.485 p<0.05) was similar to male healthy subjects, but the regression equations differed significantly in slope and intercept. Dividing controls and patients in subgroups with low, median and high net uptake rates, it was found that the frequencies of these uptake rate classes were 24.6%, 33.3%, 42.1% in controls and 38.3%, 44.7%, 17.0% in patients respectively. Patients and controls with low net uptake rate showed very similar uptake kinetics and uptake efficiencies, but the lack of a significant correlation between 5HT content and the ratio Vmax/Km differentiated patients from controls. The status of the serotonergic system, expressed as relationship between 5HT content and uptake efficiency, was very similar in patients and controls in the range of medium net uptake rate. A trend toward higher values of uptake efficiency was apparent in patients with high net uptake rate but the platelet-5HT content was similar to corresponding controls. Mean scores on the HAMD scale (total score and psychic anxiety item) were significantly higher in the low net uptake rate group of patients than in those with a high net uptake rate.

Adult↗

PubMed2000

Positive and negative mutant selection in the human histone hairpin-binding protein using the yeast three-hybrid system.

We have used the yeast three-hybrid system in a positive selection for mutants of the human histone hairpin-binding protein (HBP) capable of interacting with non-canonical hairpins and in a negative selection for loss-of-binding mutants. Interestingly, all mutations from the positive selection are located in the N- and C-terminal regions flanking a minimal RNA-binding domain (RBD) previously defined between amino acids 126 and 198. Further, in vitro binding studies demonstrate that the RBD, which shows no obvious similarity to other RNA-binding motifs, has a relaxed sequence specificity compared to full-length HBP, allowing it to bind to mutant hairpin RNAs not normally found in histone genes. These findings indicate that the sequences flanking the RBD are important for restricting binding to the highly conserved histone hairpin structure. Among the loss-of-binding mutations, about half are nonsense mutations distributed throughout the N-terminal part and the RBD whereas the other half are missense mutations restricted to the RBD. Whereas the nonsense mutations permit a more precise definition of the C-terminal border of the RBD, the missense mutations identify critical residues for RNA binding within the RBD.

Amino Acid Sequence↗

PubMed2000

Amino acid neurotransmitter metabolism in neurones and glia following kainate injection in rats.

Limbic seizure was induced in rats by intraperitoneal injection of the glutamate receptor agonist kainic acid. After 14 days [1-13C]glucose and [1,2-13C]acetate were injected subcutaneously and the rats killed 15 min later. Analysis of brain extracts was performed using 13C-magnetic resonance spectroscopy and high performance liquid chromatography. No significant differences between the two groups of rats were found for label concentration in blood or total metabolite tissue levels. Only astrocytes are able to utilize acetate as a substrate, whereas glucose is thought to be metabolized predominantly in the neuronal tricarboxylic acid cycle. Thus information about neuronal and astrocytic metabolism could be obtained in the same animal. A significant increase in label derived from [1-13C]glucose was observed in metabolites such as glutamate, gamma-aminobutyric acid, aspartate, and succinate (all of which are mainly labelled in neurones). The increased labelling of glutamine in epileptic rats might be due to transfer of labelled glutamate from neurones to astrocytes. Astrocytic metabolism of acetate and transfer of glutamine to neurones were not affected. The results suggest that increased neuronal activity 2 weeks following epileptic seizures produces increased amino acid turnover in neurones. Changes in astrocytic metabolism were not detected.

Animals↗

PubMed2000

A conformational switch controlling HIV-1 morphogenesis.

Assembly of infectious human immunodeficiency virus type 1 (HIV-1) proceeds in two steps. Initially, an immature virus with a spherical capsid shell consisting of uncleaved Gag polyproteins is formed. Extracellular proteolytic maturation causes rearrangement of the inner virion structure, leading to the conical capsid of the infectious virus. Using an in vitro assembly system, we show that the same HIV-1 Gag-derived protein can form spherical particles, virtually indistinguishable from immature HIV-1 capsids, as well as tubular or conical particles, resembling the mature core. The assembly phenotype could be correlated with differential binding of the protein to monoclonal antibodies recognizing epitopes in the HIV-1 capsid protein (CA), suggesting distinct conformations of this domain. Only tubular and conical particles were observed when the protein lacked spacer peptide SP1 at the C-terminus of CA, indicating that SP1 may act as a molecular switch, whose presence determines spherical capsid formation, while its cleavage leads to maturation.

Animals↗

PubMed2000

Synthesis of differentially protected N-acylated reduced pseudodipeptides as building units for backbone cyclic peptides.

Backbone cyclization has become an important method for generating or stabilizing the bioactive conformation of peptides without affecting the amino acid side-chains. Up to now, backbone cyclic peptides were mostly synthesized with bridges between N-amino- and N-carboxy-functionalized peptide bonds. To study the influence of a more flexible backbone on the biological activity, we have developed a new type of backbone cyclization which is achieved via the N-functionalized moieties of acylated reduced peptide bonds. As described in our previous publications, the formation of N-functionalized dipeptide units facilitates the peptide assembly compared with the incorporation of N-alkyl amino acids. Besides the racemization-free synthesis of Fmoc-protected pseudodipeptide esters with reduced peptide bonds, the new type of backbone modification allows the use of a great variety of omega-amino- and alpha,omega-dicarboxylic acids differing in chain length and chemical properties. Best results for the coupling of the omega-amino- and alpha,omega-dicarboxylic acids to the reduced peptide bond were obtained by the formation of mixed anhydrides with alkyl chloroformates. Whereas the protecting group combination of Z/OBzl in the dipeptide unit and Boc/OtBu for the N-functionalized moiety leads to the formation of 2-ketopiperazine during hydrogenation, the combination of Fmoc/OtBu and Alloc/OAll is very suitable for the synthesis of backbone cyclic peptides on solid support.

Acylation↗

PubMed2000

Association of genotypes affecting the expression of interleukin-1beta or interleukin-1 receptor antagonist with osteoarthritis.

OBJECTIVE: The majority of cytokines and growth factors known to be involved in cartilage metabolism are synthesized by the chondrocytes themselves. They are up-regulated in osteoarthritic (OA) cartilage, resulting in 2 opposite phenotypes, TNFalpha(high) and TNFalpha(low), that are characterized by an elevated number of tumor necrosis factor alpha (TNFalpha)-positive and interleukin-1beta (IL-1beta)-positive chondrocytes, respectively. To establish a hierarchy among the cytokines and growth factors expressed in articular chondrocytes, this study investigated cytokine genes for known polymorphisms that may contribute to the deregulated expression in OA cartilage. METHODS: Polymerase chain reaction techniques were performed either in a thermal cycler using standard methods or in a light cycler to analyze the frequencies of the TNFalpha (-308), IL-1 receptor antagonist (IL-1Ra) (intron 2), IL-1beta (exon 5), and IL-6 (-174) polymorphisms in 61 OA patients and 254 randomly chosen controls. RESULTS: For the TNFalpha(low) phenotype, a statistically significant association was found with the less frequent allele of IL-1beta, which carries a single-basepair substitution in exon 5 and may contribute to the characteristic increase in IL-beta-positive chondrocytes. In contrast, the TNFalpha(high) phenotype was significantly associated with the less frequent allele of IL-1Ra, which carries two 86-bp repeats in the second intron and is assumed to lead to an elevated expression of the antagonist. CONCLUSION: These results point to an association between the IL-1beta polymorphism and the TNFalpha(high) phenotype and between the IL-1Ra polymorphism and the TNFalpha(low) phenotype found in OA. Both associations suggest that IL-1beta may be more important than TNFalpha for the regulation of cytokine and growth factor expression in articular chondrocytes.

Alleles↗

PubMed2000

Acidic pH inhibits non-MHC-restricted killer cell functions.

Immunotherapeutic strategies in advanced stages of solid tumors have generally met with little success. Various mechanisms have been discussed permitting the escape of tumor cells from an effective antitumoral immune response. Solid tumors are known to develop regions with acidic interstitial pH. In a recent study performed in the human system, we were able to demonstrate that non-MHC-restricted cytotoxicity is inhibited by an acidic microenvironment. To get more insight into the mechanisms leading to this reduced cytotoxic activity, we have now investigated the influence of an acidic extracellular pH (pH(e)) on the killing process in detail. Unstimulated PBMC and LAK cells were used as effector cells. Both populations are able to kill tumor cells in a MHC-independent manner via perforin/granzymes or TNFalpha, whereas only IL-2-activated cells can use the killing pathway via Fas/FasL. We studied the influence of a declining pH(e) on the different killing pathways against TNFalpha-sensitive and -resistant, as well as Fas-positive and -negative, target cells. Experiments in the absence of extracellular Ca(2+) were used to discriminate the Ca(2+)-dependent perforin-mediated killing. Here we show that the release of perforin/granzyme-containing granules, the secretion of TNFalpha, and also the cytotoxic action of Fas/FasL interaction or of membrane-bound TNFalpha were considerably inhibited by declining pH(e). Furthermore, the secretion of the activating cytokine IFNgamma, as well as the release of the down-regulating cytokines IL-10 and TGF-beta(1), was strictly influenced by surrounding pH. As a pH(e) of 5.8 resulted in a nearly complete loss of cytotoxic effector cell functions without affecting their viability, we investigated the influence of pH(e) on basic cellular functions, e.g. , mitochondrial activity and regulation of intracellular pH. We found an increasing inhibition of both functions with declining pH(e). Therefore, an acidic pH(e) obviously impairs fundamental cellular regulation, which finally prevents the killing process. In summary, our data show a strict pH(e) dependence of various killer cell functions. Thus, an acidic microenvironment within solid tumors may contribute to the observed immunosuppression in vivo, compromising antitumoral defense and immunotherapy in general, respectively.

Acids↗

PubMed2000

[Donor site problems after anterior cruciate ligament reconstruction with the middle third of the patellar ligament].

In a retrospective study we examined the clinical and sonographic changes after anterior cruciate ligament reconstruction with lig. patellae. 51 patients were evaluated clinically and sonographically after arthroscopically assisted ACL-reconstruction with a bone-patella tendon 3-6 years (mean 4.3 years) postoperatively. Certainly 18 patients (35%) reported about an anterior knee pain, but only 2 patients (4%) complained about pain during activities of daily living and 3 patients (6%) about pain during slight sports activities. Retropatellar crepitations was found in 24 patients (47%) on the operated side and at 11 patients (22%) on the non operated side. Twenty nine patients (57%) complained about a discomfort or pain when kneeling on the operated side. In 13 patients (26%) sonography showed a shortening of the patella ligament by 4 mm or more. Only few patients are strongly limited in their activity by the anterior knee pain. Neither our results nor the literature give evidence, that the tendon defect is the underlying cause of this pain syndrome. However, the number of patients with pain during kneeling on the operated side was relatively high. The semitendinosus gracilis graft should be considered for patients who have to knee during working or recreational activities.

Anterior Cruciate Ligament↗

PubMed2000

Reliability and interobserver variability in radiological patellar height ratios.

This study evaluated the reliability and interobserver variability of five patellar height ratios as measured by two examiners on standard radiographs: Insall-Salvati (IS), modified Insall-Salvati (MIS), Blackburne-Peel (BP), Caton-Deschamps (CD), and Labelle-Laurin (LL). Plain lateral radiographs with a knee flexion angle of 20 degrees for IS, MIS, BP, and CD ratios and 90 degrees for the LL method of 22 knees of 21 patients with varying pathological knee conditions were analyzed. Statistical results revealed a low interobserver variability with high correlation coefficients (0.86 for IS, 0.82 for MIS, 0.86 for BP, 0.92 for CD, and 0.81 for LL; P > 0.3) and low mean interobserver errors. However, regarding the reliability of the radiographic results of the different methods for patella alta, baja, or norma we found varying results in 68% of the patients. In two patients the patellar height was classified as alta, norma, or baja depending on the ratio used. Regarding the definitions of patellar height used by the authors of these methods, we found the lowest number of normal patellae with the IS ratio and no patella alta for the CD ratio. The LL method revealed the highest number of patella alta. The BP ratio showed intermediate results for both patella alta and baja, being the most moderate method. This study showed that there was a good interobserver reliability for the evaluation of patellar height according to the common radiological ratios. However, the high frequency of differing results between the different radiographic ratios showed that patellar height classification as "alta," "norma," or "baja" depends heavily on the chosen index. The differing results were due mainly to the normative patellar height data and to anatomical differences. Based on these findings we recommend a ratio using the articular surface of the patella in relation to the joint line. We recommend the BP method because it revealed the lowest interobserver variability and discriminated best among the groups alta, norma, and baja.

Adolescent↗