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Biomedical subjects

U Fischer

Publications and source records attributed to U Fischer.

At least 145 records · Page 8Linked to original sources
PubMed1997

The spinal muscular atrophy disease gene product, SMN, and its associated protein SIP1 are in a complex with spliceosomal snRNP proteins.

Spinal muscular atrophy (SMA), one of the most common fatal autosomal recessive diseases, is characterized by degeneration of motor neurons and muscular atrophy. The SMA disease gene, termed Survival of Motor Neurons (SMN), is deleted or mutated in over 98% of SMA patients. The function of the SMN protein is unknown. We found that SMN is tightly associated with a novel protein, SIP1, and together they form a specific complex with several spliceosomal snRNP proteins. SMN interacts directly with several of the snRNP Sm core proteins, including B, D1-3, and E. Interestingly, SIP1 has significant sequence similarity with Brr1, a yeast protein critical for snRNP biogenesis. These findings suggest a role for SMN and SIP1 in spliceosomal snRNP biogenesis and function and provide a likely molecular mechanism for the cause of SMA.

3T3 Cells↗
PubMed1997

The SMN-SIP1 complex has an essential role in spliceosomal snRNP biogenesis.

Spinal muscular atrophy (SMA) is an often fatal neuromuscular disease that has been directly linked to the protein product of the Survival of Motor Neurons (SMN) gene. The SMN protein is tightly associated with a novel protein, SIP1, and together they form a complex with several spliceosomal snRNP proteins. Here we show that the SMN-SIP1 complex is associated with spliceosomal snRNAs U1 and U5 in the cytoplasm of Xenopus oocytes. Antibodies directed against the SMN-SIP1 complex strongly interfere with the cytoplasmic assembly of the common (Sm) snRNP proteins with spliceosomal snRNAs and with the import of the snRNP complex into the nucleus. Thus, the SMN-SIP1 complex is directly involved in the biogenesis of spliceosomal snRNPs. Defects in spliceosomal snRNP biogenesis may, therefore, be the cause of SMA.

Antibodies, Monoclonal↗
PubMed1997

HIV-1 infection of non-dividing cells: evidence that the amino-terminal basic region of the viral matrix protein is important for Gag processing but not for post-entry nuclear import.

Human immunodeficiency virus type-1 (HIV-1) is able to infect non-dividing cells such as tissue macrophages productively because post-entry viral nucleoprotein complexes are specifically imported into the nucleus in the absence of mitosis. Although it has been proposed that an amino-terminal region of the viral matrix (MA, p17Gag) protein harbors a basic-type nuclear localization sequence (NLS) that contributes to this process, utilization of three distinct nuclear import assays failed to provide any direct supporting evidence. Instead, we found that disruption of this region (26KK-->TT) reduces the rate at which the viral Gag polyprotein (p55Gag) is post-translationally processed by the viral protease. Consistent with the fact that appropriate proteolytic processing is essential for efficient viral growth in all cell types, we also show that the 26KK-->TT MA mutation is equivalently deleterious to the replication of a primary macrophage-tropic viral isolate in cultures of non-dividing and dividing cells. Taken together, these observations suggest that proteins other than MA supply the NLS(s) that enable HIV-1 to infect non-dividing cells.

Amino Acid Sequence↗
PubMed1997

A role for the M9 transport signal of hnRNP A1 in mRNA nuclear export.

Among the nuclear proteins associated with mRNAs before their export to the cytoplasm are the abundant heterogeneous nuclear (hn) RNPs. Several of these contain the M9 signal that, in the case of hnRNP A1, has been shown to be sufficient to signal both nuclear export and nuclear import in cultured somatic cells. Kinetic competition experiments are used here to demonstrate that M9-directed nuclear import in Xenopus oocytes is a saturable process. Saturating levels of M9 have, however, no effect on the import of either U snRNPs or proteins carrying a classical basic NLS. Previous work demonstrated the existence of nuclear export factors specific for particular classes of RNA. Injection of hnRNP A1 but not of a mutant protein lacking the M9 domain inhibited export of mRNA but not of other classes of RNA. This suggests that hnRNP A1 or other proteins containing an M9 domain play a role in mRNA export from the nucleus. However, the requirement for M9 function in mRNA export is not identical to that in hnRNP A1 protein transport.

Animals↗
PubMed1997

Prediction of in vivo drug interaction from in vitro systems exemplified by interaction between verapamil and cimetidine using human liver microsomes and primary hepatocytes.

Emphasis on drug safety is increasing as newly developed drugs become more potent. Interest in the prediction and description of drug interactions is growing accordingly. The study of potential interactions at a very early stage of drug development requires suitable in vitro models that describe drug interactions both qualitatively and quantitatively. The purpose of the work described here was to help assess the predictive value of in vitro drug interaction tests with liver microsomes and hepatocytes by means of the interaction between verapamil and cimetidine. The in vitro inhibition of verapamil metabolism by cimetidine observed during the studies was quantitatively similar to the results reported in published clinical studies after intravenous application. Studies using liver microsome fractions showed that the intrinsic clearances for the formation of various metabolites could be used to predict drug interactions. In addition, work with hepatocyte cultures revealed that an in vitro system covering both phase I and phase II reactions should be included in such studies to permit quantitative prediction of the various metabolic pathways. Both human hepatocyte cultures and human microsomes offer certain advantages for predicting the degree of drug metabolism and interactions in humans at the biotransformation level. Therefore, it seems likely that the simultaneous application of both systems will yield conclusions that most closely approximate the situation in humans.

Animals↗
PubMed1997

[MRI-assisted biopsy and localization of the breast].

If suspicious lesions found with MR imaging cannot be visualized by either mammography or ultrasound, MR imaging--based guidance systems are needed to guide needle biopsy or to allow localization of the lesion before surgery. The authors give an overview of the advantages and disadvantages of biopsy devices presented by different working groups. Furthermore, MR-compatible needle equipment for interventions of the breast is demonstrated. The angulation of the needle and the type of sequence are the most important factors for signal loss due to susceptibility. The strategy in special problem cases (multicentricity, bilateral lesions) is discussed. Control MR imaging within the first week after open biopsy is the best way to document the complete excision of a suspicious hypervascularized lesion after MR-guided wire localization. At our institute, percutaneous biopsy (36 interventions) revealed benign findings in 67% and malignant lesions in 25% of cases. Three biopsies were insufficient. Histology after MR-guided wire localization (136 interventions) showed benign findings in 51% and malignancy in 49% of cases. The suspicious lesion was missed by the surgeon in three cases. We perform MR-guided interventions of the breast routinely in indicated cases.

Biopsy, Needle↗
PubMed1997

Penetration of ciprofloxacin, norfloxacin and ofloxacin into the aqueous humours of patients by different topical application modes.

OBJECTIVE: A prospective study was undertaken to determine the transcorneal penetration of three topically applied fluoroquinolones into aqueous humour. METHODS: Two hundred and twenty-four patients undergoing cataract extraction received 0.3% ciprofloxacin, norfloxacin or ofloxacin eye drops by two different administration modes with different frequencies and intervals of application. At the beginning of cataract extraction (0.5-3 h after the last drop), 50-100 microliters aqueous fluid was aspirated from the anterior chamber and immediately stored at -80 degrees C. Antibiotic concentrations were measured using high-performance liquid chromatography. RESULTS: Generally, topical ofloxacin and ciprofloxacin yielded aqueous humour levels higher than topical norfloxacin. The highest concentrations of all tested fluoroquinolones were measured after using an application mode, in which one drop was given every 15 min between 0600 hours and 0800 hours, prior to operation. When applied by this mode, ciprofloxacin achieved a mean aqueous level of 0.380 (+/- 0.328) microgram.ml-1 (range 0.033-1.388 micrograms.ml-1), norfloxacin 0.182 (0.118) microgram.ml-1 (range 0.038-0.480 microgram.ml-1) and ofloxacin 0.564 (0.372) microgram.ml-1 (range 0.064-1.455 micrograms.ml-1). These mean concentrations were above the minimum inhibitory concentration (MIC90), concentrations required for inhibition of 90% of pathogen strains in vitro of gram-negative bacteria, such as Proteus mirabilis and Escherichia coli. Therapeutic values above the MIC90 of Staphylococcus epidermidis, the pathogen causing eye infections most frequently, were reached by 67.5% of patients after ofloxacin and by 41% after ciprofloxacin, but never after norfloxacin treatment. CONCLUSION: Of the currently available topical fluoroquinolones, ofloxacin achieved the highest aqueous humour concentration. This fluoroquinolone may be an useful ophthalmic agent for topical antibacterial management, but it does not seem to be prophylactically effective against Streptococcus pneumoniae or Pseudomanas aeruginosa.

Administration, Topical↗
PubMed1997

Prognostic value of contrast-enhanced MR mammography in patients with breast cancer.

The objective of this study was to evaluate the prognostic value of contrast-enhanced MR mammography in patients with breast cancer. A total of 190 patients with breast cancer (37 noninvasive carcinomas, 153 invasive carcinomas) underwent dynamic contrast-enhanced MR mammography preoperatively. Using 1.5-T unit, T1-weighted sequences (2D FLASH) were obtained repeatedly one time before and five times after IV administration of 0.1 mmol gadopentetate-dimeglumine per kilogram body weight. The findings on MR imaging were correlated with histopathologically defined prognostic factors (histological type, tumor size, tumor grading, metastasis in lymph nodes). In addition, immunohistochemically defined prognostic factors (c-erbB-1, c-erbB-2, p53, Ki-67) were correlated with the signal increase on MR mammogram in 40 patients. There was no significant correlation between the findings on MR mammography and the histopathological type of carcinoma, the grading, and the lymphonodular status. Noninvasive carcinomas showed a higher rate of moderate (38 %) or low (27 %) enhancement on MR imaging than invasive carcinomas (6 and 3 %). The results on MR mammography and the results of immunohistochemical stainings did not correlate significantly. Noninvasive carcinomas showed significantly lower enhancement than invasive carcinomas. However, the signal behavior of contrast-enhanced MR mammography is not related to established histopathological prognostic parameters as subtyping, grading, nodal status, and the expression of certain oncogenes/tumor suppressor genes.

Biomarkers, Tumor↗
PubMed1997

Identification of an amplified gene cluster in glioma including two novel amplified genes isolated by exon trapping.

Gene amplification, which occurs in more than 50% of malignant gliomas, is considered to play a pivotal role in tumorigenesis. There are, however, few studies aimed toward the isolation of novel genes from amplified sequences. Previously, we reported amplification of the protooncogene MET (hepatocyte growth factor receptor; 7q31) in more than 20% of glioblastomas. For an approximate size estimation of the amplification unit we analyzed three glioblastomas all of which carried an amplified MET gene, by Southern blot analysis and/or competitive polymerase chain reaction using eight DNA markers. Although the extent of the amplified domain varied, the close vicinity of the MET gene was the only region consistently amplified in these glioblastomas. A yeast artificial chromosome (YAC) contig of 900 kb was refined spanning the amplified region flanking the MET gene. The YAC inserts were subcloned into 59 cosmids, which were used for exon trapping. Eight sequences were identical to parts of the genes MET and CAPZA2 (human actin capping protein alpha-subunit). Two newly identified exons and the CAPZA2 exons were amplified in tumor TX3095, which retains an amplified MET gene. The new exons were localized close to MET and CAPZA2. Characterization of the clones, which were termed glioma-amplified sequence (GAS)7-1 and GAS7-2, showed an open reading frame and a different expression pattern in multiple human tissues. This study reports the identification of a cluster of amplified genes including two novel genes in a region amplified in more than 20% of glioblastomas.

Actin Capping Proteins↗
PubMed1997

[Results of a contrast-medium supported 3D MR-angiography in respiratory arrest following optimization of contrast medium bolus].

PURPOSE: Reduction of the contrast material volume by optimised bolus administration during a breath-hold 3D MR angiography and its clinical value. MATERIALS AND METHODS: Breath-hold ultrafast 3D gadolinium-enhanced MR angiography (TR 5 ms, TE 2 ms, FA 20 degrees) of the thoracic and abdominal aorta was performed in 50 patients and correlated with an i.a. DSA. 25 patients (group 1) were examined with a contrast material volume of 40 ml Gd-DTPA and three successive acquisitions at fixed intervals (25, 53 and 81 s) after start of the contrast material injection. Another group of 25 patients (group 2) received only 20 ml Gd-DTPA and the start of the MR acquisition was determined individually by prior evaluation of the contrast material transit times after injection of a test bolus. The signal-to-noise (S/N) and contrast-to-noise (C/N) ratios were compared and a subjective image quality rating (0-3) by three reviewers was achieved in both groups. RESULTS: A total of 37 vascular pathologies were correctly detected by MR angiography compared to i.a. DSA. The grading of stenoses was overestimated in some cases. The S/N and C/N were higher in group 2 (63.2 and 50.1) than in group 1 (58.0 and 38.9). The subjective ratings also showed better results in group 2 (2.76) than in group 1 (2.20). CONCLUSION: The ultrafast gadolinium-enhanced 3D MR angiography allowed a reliable visualisation of the thoracic and abdominal aorta and its branches in a single breath-hold. An optimised examination with a reduced contrast material volume can be achieved by an individual adaptation of the MR acquisition to contrast material administration after measurement of the contrast material transit times.

Aged↗
PubMed1997

Cloning of a novel transcription factor-like gene amplified in human glioma including astrocytoma grade I.

Gene amplification, which is generally considered to occur late in tumor development, is a common feature of high grade glioma. Up until now, there have been no reports on amplification in astrocytoma grade I. In this study, we report cloning and sequencing of a cDNA termed glioma-amplified sequence (GAS41) which was identified recently in a glioblastoma cell line by microdissection-mediated cDNA capture. This technique is tailored to isolate amplified genes from human tumors. An increased copy number of GAS41 was found in glioblastoma multiforme and astrocytoma III, and at a high frequency in astrocytoma grades I and II. Sequence comparison indicates a high homology between the GAS41 protein, the yeast and human AF-9 and the human ENL proteins. Both AF-9 and ENL belong to a new class of transcription factors, indicating that GAS41 might also represent a transcription factor. With GAS41 being the first gene found with increased copy number in low grade glioma, this study provides the first evidence that gene amplification can occur in early tumor development.

Amino Acid Sequence↗
PubMed1997

cDNA cloning and chromosomal mapping of a predicted coiled-coil proline-rich protein immunogenic in meningioma patients.

There is increasing evidence that tumor expressed genes induce immune responses in cancer patients. To identify meningioma expressed antigens, we established a meningioma expression library which was screened with autologous serum. Out of 20 positive cDNA clones eight share high sequence homologies as determined by sequence analysis. These eight clones can be grouped into three classes which differ in length and which are characterized by specific sequence variations. The longest open reading frame was found to be 2412 bp encoding an immunoreactive antigen termed meningioma expressed antigen 6 (MEA6). Using five sequence specific primer pairs, somatic hybrid panel mapping revealed locations of the three classes on several human chromosomes including chromosomes 2, 3, 6, 7, 9, 13 and 14. The mapping results were confirmed by fluorescence in situ hybridization. RT-PCR showed consistent expression of all classes in several meningiomas and additional tissues using the same set of primer pairs as for chromosomal mapping. The expression data were confirmed by northern blot analysis. For the predicted amino acid sequence BLASTX revealed a homology to a human C219-reactive peptide which was previously isolated by an antibody directed against p-glycoprotein. Sequence properties of the MEA protein include an acidic activation domain, a proline-rich region and two coiled-coil domains indicating protein binding and activation functions.

Amino Acid Sequence↗
PubMed1997

RNA transport.

RNA molecules synthesized in the nucleus are transported to their sites of function throughout the eukaryotic cell by specific transport pathways. This review focuses on transport of messenger RNA, small nuclear RNA, ribosomal RNA, and transfer RNA between the nucleus and the cytoplasm. The general molecular mechanisms involved in nucleocytoplasmic transport of RNA are only beginning to be understood. However, during the past few years, substantial progress has been made. A major theme that emerges from recent studies of RNA transport is that specific signals mediate the transport of each class of RNA, and these signals are provided largely by the specific proteins with which each RNA is associated.

Animals↗
PubMed1997

Dual-phase helical CT of the kidney: value of the corticomedullary and nephrographic phase for evaluation of renal lesions and preoperative staging of renal cell carcinoma.

OBJECTIVE: Our objective was to evaluate early-phase unenhanced and late-phase contrast-enhanced helical CT in revealing renal lesions and staging renal cell carcinomas. SUBJECTS AND METHODS: Contrast-enhanced helical CT of the kidneys was performed in 145 patients who also underwent unenhanced CT. Contrast-enhanced CT was performed in the corticomedullary phase (CMP) and nephrographic phase (NP). A total of 173 lesions in 96 patients were proven histologically or cytologically. The performance of helical CT in the three study groups was compared: unenhanced and CMP enhancement, group 1; unenhanced and NP enhancement, group 2; unenhanced, CMP enhancement, and NP enhancement, group 3. Among the parameters evaluated were the sensitivity for helical CT of all 173 renal lesions and the sensitivity and specificity for the 90 malignant tumors. Also, the preoperative CT staging of the 76 renal cell carcinomas was correlated with the pathologic specimens. RESULTS: The sensitivity for detection of all renal lesions in group 1 (84%) was significantly less than in groups 2 and 3 (97% and 100%). The specificity and accuracy of helical CT in revealing renal cell carcinomas were significantly higher (p < .05) in group 3 (95% and 95%, respectively) than in groups 1 (93% and 92%, respectively) and 2 (89% and 91%, respectively). Two renal cell carcinomas were overlooked by the interpreters of the helical scans in group 1. The accuracy of preoperative CT staging of renal cell carcinomas was significantly better (p < .05) in group 3 (91%) than in groups 1 (82%) and 2 (86%). CONCLUSION: When patients underwent unenhanced helical CT, CMP helical CT, and NP helical CT, we achieved a better rate of detection and characterization of renal lesions and better preoperative staging of renal cell carcinomas than when we used either CMP helical CT or NP helical CT alone.

Adult↗
PubMed1997

Blood glucose lowering and glucagonostatic effects of glucagon-like peptide I in insulin-deprived diabetic dogs.

To establish potential effects of glucagon-like peptide I (GLP-I) on blood glucose control in insulin-deficient states, GLP-I [GLP-I(7-36) amide; 10 pmol x kg(-1) x min(-1)] was infused intravenously in six fasting, canine C-peptide-negative, chronically diabetic dogs for 8 h. Blood samples were saved for the analysis of hormones, metabolites, and turnover rates of glucose (6-(3)H-glucose), alanine (U-(14)C-alanine), and urea ((15)N(2)-urea) starting 22 h after the last subcutaneous dose of exogenous insulin. Circulating plasma GLP-I levels rose under infusion from 2.9 +/- 0.8 to 41.4 +/- 10.1 pmol/l. This was efficient to significantly reduce the preexisting diabetic hyperglucagonemia. Since in the utilized model functioning pancreatic beta-cells are lacking, GLP-I had no insulinogenic effect. Compared with control experiments in the same animals receiving saline infusion, glycemia dropped from 20.8 +/- 1.9 to 16.2 +/- 1.0 mmol/l (P < 0.05). This was in parallel to the infusion of GLP-I and was most likely caused by a decrease of elevated glucose production since overall glucose turnover decreased with no alteration in glucose metabolic clearance. Alanine turnover was significantly reduced, obviously reflecting a decline in alanine production in relation to changed muscle glucose uptake under conditions of lower glycemia and overall glucose turnover. There was, however, neither an effect of GLP-I on alanine conversion into circulating glucose nor an effect on urea production rate, indicating unchanged gluconeogenesis from amino acid precursors. We conclude that the blood glucose-lowering effect of GLP-I in an animal model of insulinopenia was shown to be due to a reduction in hepatic glucose output, possibly secondary to reduction in glucagon concentrations leading to decreased glycogenolysis. Whether GLP-I might be therapeutically useful in clinical insulin-deficient diabetes needs to be verified.

Alanine↗
PubMed1997

Primitive neuroectodermal tumor of the cervix uteri. A case report.

Primitive neuroectodermal tumors (PNET) of the female genital tract are rare and more common in the ovary, but uncommon in the cervix uteri. A 26-year-old woman presented with suspect cervical smears. The conization specimen showed a small cell non-keratinised squamous cell carcinoma with involved margins. The patient underwent radical abdominal hysterectomy and pelvic lymphonodectomy. The microscopic examination showed a densely cellular tumor of small neuroendocrine cells with scanty cytoplasm and rosettes. Immunohistochemically, the cells were slightly positive for NSE and negative for S 100, GFAP, neurofilaments, squamous cell cytokeratin 1, vimentin, desmin and leukocyte common antigen. The diagnosis of PNET, stage pT1b1,N0, M0 was made. The patient underwent adjuvant pelvic radiation. Three years later, pulmonary metastases occured. Radiation therapy of the thorax and six courses of combination chemotherapy (5-FU and cis-platinium) could not prevent tumor progression. The patient died 4.2 years after diagnosis. The autopsy showed widespread lymphatic metastases and hepatic, pulmonal and skeletal metastases and a peritoneal carcinosis. The tumors are resistent to radio- and chemotherapy, and the prognosis is generally poor. Up to 15% foci of squamous or glandular differentiation occur in or adjacent to these tumors. So the authors favor the histogenesis from a pluripotent endocervical stem cell. The neuroendocrine component of mixed tumors improve the prognosis. Therefore, it is necessary to recognize this component.

Adult↗