Biomedical subjects

C Fischer

Publications and source records attributed to C Fischer.

At least 73 records · Page 4Linked to original sources

PubMed2001

Elucidation of the function of two glycosyltransferase genes (lanGT1 and lanGT4) involved in landomycin biosynthesis and generation of new oligosaccharide antibiotics.

BACKGROUND: The genetic engineering of antibiotic-producing Streptomyces strains is an approach that became a successful methodology in developing new natural polyketide derivatives. Glycosyltransferases are important biosynthetic enzymes that link sugar moieties to aglycones, which often derive from polyketides. Biological activity is frequently generated along with this process. Here we report the use of glycosyltransferase genes isolated from the landomycin biosynthetic gene cluster to create hybrid landomycin/urdamycin oligosaccharide antibiotics. RESULTS: Production of several novel urdamycin derivatives by a mutant of Streptomyces fradiae Tü2717 has been achieved in a combinatorial biosynthetic approach using glycosyltransferase genes from the landomycin producer Streptomyces cyanogenus S136. For the generation of gene cassettes useful for combinatorial biosynthesis experiments new vectors named pMUNI, pMUNII and pMUNIII were constructed. These vectors facilitate the construction of gene combinations taking advantage of the compatible MunI and EcoRI restriction sites. CONCLUSIONS: The high-yielding production of novel oligosaccharide antibiotics using glycosyltransferase gene cassettes generated in a very convenient way proves that glycosyltransferases can be flexible towards the alcohol substrate. In addition, our results indicate that LanGT1 from S. cyanogenus S136 is a D-olivosyltransferase, whereas LanGT4 is a L-rhodinosyltransferase.

Aminoglycosides↗

PubMed2001

Non-random radial higher-order chromatin arrangements in nuclei of diploid human cells.

A quantitative comparison of higher-order chromatin arrangements was performed in human cell types with three-dimensionally (3D) preserved, differently shaped nuclei. These cell types included flat-ellipsoid nuclei of diploid amniotic fluid cells and fibroblasts and spherical nuclei of B and T lymphocytes from peripheral human blood. Fluorescence in-situ hybridization (FISH) was performed with chromosome paint probes for large (#1-5) and small (#17-20) autosomes, and for the two sex chromosomes. Other probes delineated heterochromatin blocks of numerous larger and smaller human chromosomes. Shape differences correlated with distinct differences in higher order chromatin arrangements: in the spherically shaped lymphocyte nuclei we noted the preferential positioning of the small, gene dense #17, 19 and 20 chromosome territories (CTs) in the 3D nuclear interior--typically without any apparent connection to the nuclear envelope. In contrast, CTs of the gene-poor small chromosomes #18 and Y were apparently attached at the nuclear envelope. CTs of large chromosomes were also preferentially located towards the nuclear periphery. In the ellipsoid nuclei of amniotic fluid cells and fibroblasts, all tested CTs showed attachments to the upper and/or lower part of the nuclear envelope: CTs of small chromosomes, including #18 and Y, were located towards the centre of the nuclear projection (CNP), while the large chromosomes were positioned towards the 2D nuclear rim. In contrast to these highly reproducible radial arrangements, 2D distances measured between heterochromatin blocks of homologous and heterologous CTs were strikingly variable. These results as well as CT painting let us conclude that nuclear functions in the studied cell types may not require reproducible side-by-side arrangements of specific homologous or non-homologous CTs. 3D-modelling of statistical arrangements of 46 human CTs in spherical nuclei was performed under the assumption of a linear correlation between DNA content of each chromosome and its CT volume. In a set of modelled nuclei, we noted the preferential localization of smaller CTs towards the 3D periphery and of larger CTs towards the 3D centre. This distribution is in clear contrast to the experimentally observed distribution in lymphocyte nuclei. We conclude that presently unknown factors (other than topological constraints) may play a decisive role to enforce the different radial arrangements of large and small CTs observed in ellipsoid and spherical human cell nuclei.

Amniotic Fluid↗

PubMed2001

Enrichment of mutant KRAS alleles in pancreatic juice by subtractive iterative polymerase chain reaction.

SUMMARY: The detection of mutant tumor genes holds great promise for an early diagnosis of primary tumors and residual malignant disease. When few tumor cells are present with an excess of nonmalignant cells of the same lineage, the excess of wild-type alleles over mutant tumor alleles presents an analytical problem. The subtractive iterative PCR (siPCR) assay presents a new approach to solving this problem. To achieve an enrichment of mutant alleles, wild-type alleles are removed by differential hybridization to complementary oligonucleotides spanning the region of the gene in which point mutations are expected. The nonbound fraction is reamplified by PCR. By iterating this process, mutant alleles can be detected in the presence of an excess of wild-type alleles with high sensitivity. To prove the feasibility of siPCR, pancreatic juice samples were analyzed for KRAS mutations. Pancreatic juice obtained from patients with pancreatic carcinoma or chronic pancreatitis during endoscopic retrograde cholangiopancreatography was analyzed for point mutations in codons 12 and 13 of the KRAS gene. In each of six samples from tumor patients, mutations in codon 12 were detected. One of nine samples from patients with chronic pancreatitis scored positive.

Alleles↗

PubMed2001

Processing of facial emotional expression: spatio-temporal data as assessed by scalp event-related potentials.

Event-related potentials (ERPs) were recorded in 10 adult volunteers, who were asked to view pictures of faces with different emotional expressions, i.e. fear, happiness, disgust, surprise and neutral expression [Ekman, P. & Friesen, W.V. (1975). Pictures of Facial Affect. Consulting Psychologist Press, Palo Alto, CA]. ERPs were recorded during two different tasks with the same stimuli. Firstly, subjects were instructed to pay attention to the gender of the faces by counting males or females. Secondly, they had to focus on facial expressions by counting faces who looked surprised. The classical scalp 'face-related potentials', i.e. a vertex-positive potential and a bilateral temporal negativity, were recorded 150 ms after the stimulus onset. Significant differences were found, firstly between late-latency ERPs to emotional faces and to neutral faces, between 250 and 550 ms of latency and, secondly, among the ERPs to the different facial expressions between 550 and 750 ms of latency. These differences appeared only during the expression discrimination task, not during the gender discrimination task. Topographic maps of these differences showed a specific right temporal activity related to each emotional expression, some particularities being observed for each expression. This study provides new data concerning the spatio-temporal features of facial expression processing, particularly a late-latency activity related to specific attention to facial expressions.

Adult↗

PubMed2001

Asymmetrical localization of benzodiazepine receptors in the human auditory cortex.

In humans, administration of benzodiazepines (BZD) has been shown to have an asymmetrical effect on the medial olivocochlear system. Indeed, a decrease of evoked otoacoustic emission suppression by contralateral acoustic stimulation, which explores the medial olivocochlear efferent system, was observed in the right ear, with no left ear effect. This result suggests a possible left-right auditory pathway BZD receptor asymmetry. Given the anatomical link between auditory centers and the medial olivocochlear system, the existence of a larger volume of cortical connecting fibers in the left hemisphere, and the possible link between BZD receptor density and neuronal density, we tested the hypothesis of an asymmetrical localization of BZD receptors in the auditory system in 10 right-handed subjects using [11C]flumazenil positron emission tomography. Semi-quantitative measurements of flumazenil binding were evaluated in Heschl's gyrus showing a left-right asymmetry in favor of left auditory cortex. This result indicates a higher density of neurons in left auditory cortex. The possible link between neurochemical asymmetry and functional asymmetry, and the perceptual outcome of BZD administration, will be discussed.

Adult↗

PubMed2001

Serotonin receptor gene HTR3A variants in schizophrenic and bipolar affective patients.

Serotonin receptor genes have always been considered excellent candidate genes in the aetiology of neurogenetic diseases. In this study, we assessed sequence variations of the HTR3A gene. For this purpose, we established exon-specific primers and analysed DNA samples from 165 unrelated individuals including 70 schizophrenic patients, 48 patients with bipolar affective disorder and 47 healthy control persons using polymerase chain reaction/single-strand conformational polymorphism analysis. We discovered six sequence variants, five of which represent polymorphisms. These polymorphisms could not be associated with schizophrenia and bipolar affective disorder (P = 0.055-1). We also detected a missense mutation in exon 9 in a schizophrenic patient at a conserved position (Pro391Arg). To determine the incidence of this substitution an extended set of 358 schizophrenic patients and 155 control individuals was investigated. The Pro391Arg mutation was not detected in these schizophrenic patients and controls screened. However, a second missense mutation (Arg344His) was detected in one schizophrenic patient, but not in any of the controls. These results suggest that the observed mutations in HTR3A are rare and therefore do not play a major role in the aetiology of the disorder. Further studies are needed to support the hypothesis that HTR3A may contribute to the schizophrenia in these patients.

Adult↗

PubMed2001

Association between the 5' UTR variant C178T of the serotonin receptor gene HTR3A and bipolar affective disorder.

Serotonin receptor type 3 is a ligand-gated ion channel implicated in behavioural disorders. Our objective was to identify nucleotide variants in a specific portion of the 5' region of the serotonin receptor gene (HTR3A) containing upstream open reading frames (uORFs) and to investigate their effect on bipolar disease. Mutations in uORFs have been recently shown to cause disease by changing expression on the translational level. We identified one polymorphism, C195T, and one missense mutation, C178T (Pro16Ser) within an upstream open reading frame. No significant association was found between the C195T polymorphism and bipolar affective disorder. A significant association was, however, found between the variant C178T in 156 patients with bipolar disorder compared to 156 healthy controls (P = 0.00016). To investigate the relevance of this variant on gene expression, luciferase reporter constructs containing the C178T (Pro16Ser) allele were established and compared to the C178T plus C195T and wild-type alleles. Reporter constructs containing the C178T (Pro16Ser) allele drove 245% and 138% expression compared to the wild-type allele. These findings show that the C178T(Pro16Ser) variant in HTR3A may represent a functional variant and affect the susceptibility to bipolar disorder.

5' Untranslated Regions↗

PubMed2001

Neurophysiological monitoring for epilepsy surgery: the Talairach SEEG method. StereoElectroEncephaloGraphy. Indications, results, complications and therapeutic applications in a series of 100 consecutive cases.

OBJECT OF THE STUDY: In some candidates for epilepsy surgery in whom the decision to operate is difficult to make, invasive presurgical investigations, namely depth electrode recordings, may be needed. The SEEG (StereoElectroEncephaloGraphy) method consists of stereotactic orthogonal implantation of depth electrodes (5 to 15, 11 on average). The object of this study is to clarify the indications for SEEG, to expose its complications, and to display its usefulness in terms of surgical strategy and results. PATIENTS AND METHODS: 100 patients, suffering from drug-resistant epilepsy and selected as candidates for surgical resection, underwent SEEG between 1996 and 2000. A total of 1,118 electrodes were implanted. For each single case, the sites of implantation of the electrodes were chosen in order to determine either the side of the onset of seizures, or the uni- or multilobar feature of them, or a possible operculo-insular propagation from a temporal onset, and also, using direct electrode stimulation, the proximity of speech or motor area. RESULTS: Complications occurred in 5 patients (2 superficial infections, 2 breakages of electrodes, and 1 intracerebral hematoma responsible for death). SEEG was helpful in most (84%) of the 100 patients to confirm or annul surgical indication, and to adjust the extent of the resection. In some cases (14%), SEEG allowed to propose a resection that might have been disputable based solely on noninvasive investigation data. For frontal epilepsy, SEEG was crucial in all cases to delineate the extent of resection. CONCLUSION: SEEG proved to be a relatively safe and a very useful method in 'difficult' candidates for epilepsy surgery. In addition, in some cases the implanted electrodes can be used to perform therapeutic RF thermocoagulation of epileptic foci or networks.

Adult↗

PubMed2001

Developing cultural competence in the baccalaureate nursing student: a population-based project with the Hutterites.

The purpose of this article is to articulate the process of educating baccalaureate students to apply culturally competent, population-based nursing care to the Hutterites. The Hutterites are a German dialect-speaking, ethnoreligious population. Campinha-Bacote's culturally competent model guided the student learning process. Groups of students developed culture-specific, population-based assessment models to identify the health-related needs of the Hutterites. One example of a Hutterite health assessment model that was derived from Dever's epidemiologic model and Purnell and Paulanka's model for cultural competence is presented. Priority health needs of Hutterite colonies are described, and examples of health programs are given. Recommendations for working with the Hutterite population as part of an undergraduate public health nursing course are put forth. The culturally congruent process of teaching and learning for nursing students can be applied to other health-related professions and adapted to other cultural contexts.

Clinical Competence↗

PubMed2001

Different binding modes of amphibian and human corticotropin-releasing factor type 1 and type 2 receptors: evidence for evolutionary differences.

The binding characteristics of corticotropin-releasing factor (CRF) type 1 (CRF(1)) and type 2 (CRF(2)) receptors from human (hCRF(1) and hCRF(2alpha)) and Xenopus (xCRF(1) and xCRF(2)) were compared using four different (125)I-labeled CRF analogs, the agonists (125)I-CRF and (125)I-sauvagine, and the antagonists (125)I-astressin ((125)I-AST) and (125)I-antisauvagine-30 ((125)I-aSVG). The hCRF(2alpha) and xCRF(2) receptors bound all four radioligands with different affinities, whereas hCRF(1) did not bind (125)I-aSVG, and xCRF(1) bound neither (125)I-sauvagine nor (125)I-aSVG. Competitive binding studies using unlabeled agonists and antagonists with hCRF(1) and hCRF(2alpha) receptors revealed that most agonists exhibited higher affinity in displacing agonist radioligands compared with displacement of antagonist radioligands. Exceptions were the agonists human and rat urocortin, which displayed high-affinity binding in the presence of either (125)I-labeled agonist or antagonist ligands. In contrast, the affinities of antagonists were independent of the nature of the radioligand. We also found that, in contrast to the mammalian CRF receptors, the affinity of ligand binding to xCRF(1) and xCRF(2) receptors strongly depended on the nature of the radioligand used for competition. For xCRF(1), competitors showed different rank order binding profiles with (125)I-CRF compared with (125)I-AST as the displaceable ligand. Similarly, binding of competitors to the xCRF(2) receptor showed markedly different profiles with (125)I-CRF as the competed ligand compared with the other radioligands. These data demonstrate that amphibian CRF receptors have distinctly different binding modes compared with their mammalian counterparts.

Animals↗

PubMed2001

Exercise and cytokines with particular focus on muscle-derived IL-6.

Exercise induces increased circulating levels of a number of cytokines. Thus, increased plasma levels of tumour necrosis factor (TNF)-alpha, interleukin (IL-1) beta, IL-1 receptor antagonist (IL-1ra), TNF-receptors (TNF-R), IL-10, IL-8, and macrophage inflammatory protein (MIP)-1 are found after strenuous exercise. The concentration of IL-6 increases up to 100 fold after a marathon race. Recently, it has been demonstrated that IL-6 is produced locally in contracting skeletal muscles and that the net release from the muscle can account for the exercise-induced increase in arterial IL-6 concentration. IL-6 more than any other cytokine is produced in large amounts in response to exercise. It is produced locally in the skeletal muscle in response to exercise, and IL-6 is known to induce hepatic glucose-output and to induce lipolysis. This indicates that IL-6 may represent an important link between contracting skeletal muscles and exercise-related metabolic changes.

Animals↗

PubMed2001

[Diagnostic criteria of multiple sclerosis: electrophysiological criteria].

We have made a review on the use of evoked potentials in multiple sclerosis (MS) for the past 30 years, in the diagnosis of MS, to disclose subclinical lesions or to assess atypical symptoms. Yet the role of evoked potentials in evaluation of multiple sclerosis has been changed since MRI is now widely and easily used for the diagnosis of MS. Evoked potentials are useful when symptoms are atypical without any objective impairment and when symptoms have already recovered at the time of clinical examination. Visual evoked potentials and somatosensory evoked potentials are widely used thanks to their diagnostic value and their ability to disclose spatial dissemination of multiple sclerosis. Evoked potentials have to be recorded in validated technical conditions such as to ensure reliability of data and have to be interpreted in reference to a population of healthy people recorded in the same conditions and in the same age range as MS patients.

Cerebral Cortex↗

PubMed2000

Abnormal pulmonary artery pressure response in asymptomatic carriers of primary pulmonary hypertension gene.

BACKGROUND: Familial primary pulmonary hypertension (PPH) is an autosomal-dominant inherited disease with incomplete penetrance and poor prognosis. This study was performed to examine whether asymptomatic carriers of a mutated PPH gene can be identified at an early stage by their pulmonary artery systolic pressure (PASP) response to exercise. METHODS AND RESULTS: Stress Doppler echocardiography during supine bicycle exercise and genetic linkage analysis were performed on 52 members of 2 families with PPH. In 4 PPH patients, the mean PASP was increased at rest (73+/-16 mm Hg). Fourteen additional family members with normal PASP at rest revealed an abnormal PASP response to exercise (from 23+/-4 to 56+/-11 mm Hg) without secondary cause (abnormal response [AR] group). Twenty-seven other members (NR group) revealed a normal PASP response (maximal pressure <40 mm Hg) to exercise (from 24+/-4 to 37+/-3 mm Hg, P<0. 0001). All 14 AR but only 2 NR members shared the risk haplotype with the PPH patients. The molecular genetic analysis supported linkage to chromosome 2q31-32 with a logarithm of the odds score of 4.4 when the 4 patients and the 14 AR members were classified as affected. CONCLUSIONS: We conclude that the pathological rise of PASP in asymptomatic family members is linked to chromosome 2q31-32 and is probably an early sign of PPH. Therefore, stress Doppler echocardiography may be a useful tool to identify persons at risk for PPH even before pulmonary artery pressures at rest are elevated.

Adolescent↗

PubMed2000

Long term follow-up of combined radiochemotherapy for locally advanced bladder carcinoma.

BACKGROUND: The 5- and 10-year survival rates and the toxicity of combined radiochemotherapy for 53 consecutive patients with locally advanced bladder carcinoma were studied in a noncomparative trial. METHODS: Between November 1986 and October 1987, 53 consecutive patients (mean age, 68 years) with muscle invasive and/or locally advanced bladder carcinoma were treated by simultaneous chemotherapy and hyperfractionated irradiation. Radiation was administered during the first to fourth week and during the ninth to tenth week as an interrupted treatment protocol. Cisplatin and epirubicin were used as radiosensitizers before radiation. The maximum dose of irradiation was 57.6 grays. RESULTS: Of 53 patients, 45 completed the planned treatment course. Causes for discontinuing therapy in 8 patients were pronounced myelosuppression (n = 2), severe gastrointestinal symptoms (n = 2), nephrotoxicity (n = 1), and severe radioproctitis (n = 1). Two additional patients stopped therapy due to vascular diseases independent of treatment-related toxicity. The overall survival for all 53 patients was 23% after 5 years and 8% after 10 years. Cause specific survival was 36% after 5 years and 29% after 10 years. Four patients are still alive after 10 years without disease progression. One of them received incomplete therapy due to toxicity. All four patients underwent transurethral resections for superficial, local tumor recurrences. CONCLUSIONS: The poor prognosis group of patients with invasive and/or locally advanced bladder carcinoma was found to have a limited disease specific survival after combined radiochemotherapy.

Adult↗

PubMed2000

Suppression of ethylnitrosourea-induced schwannoma development involves elimination of neu/erbB-2 mutant premalignant cells in the resistant BDIV rat strain.

Contrary to the response of rats of the highly sensitive inbred strain BDIX, BDIV rats are resistant to the induction of malignant schwannomas by exposure to the alkylating N-nitroso carcinogen N-ethyl-N-nitrosourea (EtNU). In BDIX rats, a point mutation at nucleotide 2012 in the transmembrane region of the neu/erbB-2 gene has proved to be a very early marker of initiated Schwann precursor cells with an elevated risk of malignant transformation, and is diagnostic of the resulting schwannomas. To gain insight into the cellular and molecular mechanisms responsible for the resistance of the BDIV strain, comparative quantitative neu mutation analyses combined with histomorphological studies were performed on the trigeminal nerves of EtNU-treated BDIV and BDIX rats as well as on their (BDIX x BDIV) F1 progeny. It was found that neu-mutant Schwann cells are initially present at comparable frequency in the trigeminal nerves of both resistant and sensitive animals. Contrasting with the progressive multiplication of mutant Schwann cells in BDIX trigeminal nerves, however, the numbers of mutant cells began to decrease during the intermediary phase of the carcinogenic process in BDIV animals, and premalignant neu-mutant cells were no longer detectable by the time BDIX rats developed full-blown trigeminal schwannomas. The resistance of BDIV rats thus involves the elimination of initiated neu-mutant Schwann cells during the postinitiation period of EtNU-induced schwannomagenesis via mechanisms that remain to be clarified.

Alleles↗

PubMed2000

Coxsackievirus infection of the pancreas: evaluation of receptor expression, pathogenesis, and immunopathology.

Coxsackievirus type B (CVB) infection of the pancreas induces a massive cellular infiltrate composed of natural killer cells, T cells, and macrophages and leads to the destruction of exocrine tissue. The physiological manifestations of pancreatic CVB infection are correlated with viral tropism; the virus infects acinar cells but spares the islets of Langerhans. Here we evaluate the mechanisms underlying pancreatic inflammation and destruction and identify the determinants of viral tropism. T-cell-mediated immunopathology has been invoked, along with direct virus-mediated cytopathicity, to explain certain aspects of CVB-induced pancreatic disease. However, we show here that in the pancreas, the extent of inflammation and tissue destruction appears unaltered in the absence of the cytolytic protein perforin; these findings exclude any requirement for perforin-mediated lysis by natural killer cells or cytotoxic T cells in CVB3-induced pancreatic damage. Furthermore, perforin-mediated cytotoxic T-cell activity does not contribute to the control of CVB infection in this organ. In addition, we demonstrate that the recently identified coxsackie-adenovirus receptor is expressed at high levels in acinar cells but is barely detectable in islets, which is consistent with its being a major determinant of virus tropism and, therefore, of disease. However, further studies using various cell lines of pancreatic origin reveal secondary determinants of virus tropism.

Animals↗

PubMed2000

A newly created splice donor site in exon 25 of the MyBP-C gene is responsible for inherited hypertrophic cardiomyopathy with incomplete disease penetrance.

BACKGROUND: Hypertrophic cardiomyopathy is a myocardial disorder resulting from inherited sarcomeric dysfunction. We report a mutation in the myosin-binding protein-C (MyBP-C) gene, its clinical consequences in a large family, and myocardial tissue findings that may provide insight into the mechanism of disease. METHODS AND RESULTS: History and clinical status (examination, ECG, and echocardiography) were assessed in 49 members of a multigeneration family. Linkage analysis implicated the MyBP-C gene on chromosome 11. Myocardial mRNA, genomic MyBP-C DNA, and the myocardial proteins of patients and healthy relatives were analyzed. A single guanine nucleotide insertion in exon 25 of the MyBP-C gene resulted in the loss of 40 bases in abnormally processed mRNA. A 30-kDa truncation at the C-terminus of the protein was predicted, but a polypeptide of the expected size ( approximately 95 kDa) was not detected by immunoblot testing. The disease phenotype in this family was characterized in detail: only 10 of 27 gene carriers fulfilled diagnostic criteria. Five carriers showed borderline hypertrophic cardiomyopathy, and 12 carriers were asymptomatic, with normal ECG and echocardiograms. The age of onset in symptomatic patients was late (29 to 68 years). In 2 patients, outflow obstruction required surgery. Two family members experienced premature sudden cardiac death, but survival at 50 years was 95%. CONCLUSIONS: Penetrance of this mutation was incomplete and age-dependent. The large number of asymptomatic carriers and the good prognosis support the interpretation of benign disease.

Adult↗

PubMed2000

2,2'-bipyridine lariat calixcrowns: a new class of encapsulating ligands forming highly luminescent Eu3+ and Tb3+ complexes

A new class of calix[4]arene crown ethers with one or two bipyridines appended to the polyether ring (lariat calixcrowns) have been designed and synthesized; the luminescence properties of their Eu3+ and Tb3+ complexes have been studied in acetonitrile. In this solvent, long lifetimes for the metal emitting states and high metal-luminescence intensities obtained upon ligand excitation have been observed in both Eu3+ and Tb3+ complexes. The association constants in methanol have been determined for some of the complexes studied.

Journal Article↗