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Biomedical subjects

A Schön

Publications and source records attributed to A Schön.

At least 19 recordsLinked to original sources
PubMed2002

[Sonographic diagnosis of congenital dacryocystocele].

AIM: Congenital obstruction of the nasolacrimal drainage system occurs quite commonly. The reason is usually an impaired canalization at the distal end of the nasolacrimal duct with a residual membrane between the duct and the nasal cavity. Dacryocystocele is believed to result from a concomitant upper and lower system obstruction, causing fluid accumulation and distension of the lacrimal sac. The patient presents at birth with a tense, blue-grey swelling located just below the medial canthal tendon. The differential diagnosis for dacryocystocele includes haemangioma, encephalocele, glioma, dermoid cysts and malignant processes. MATERIAL AND METHODS: We demonstrate five typical cases to describe the sonographic features of dacryocystocele. RESULTS: Ultrasound is a simple, straight forward and gentle method to reliably distinguish dacryocystoceles from other pathologies. A sedation of the patient is not necessary. The sonographic appearance of a cystic mass medial and inferior of the orbit communicating with the dilated nasolacrimal duct as well as the typical content of fluid and debris was diagnostic of a nasolacrimal mucocele or dacryocystocele. Other more invasive imaging techniques as CT-scans and MRI are of benefit only if there is any doubt about the diagnosis.

Dacryocystitis↗
PubMed2001

The first phytoplasma RNase P RNA provides new insights into the sequence requirements of this ribozyme.

A high variability of RNase P RNA structures is seen among members of the Mycoplasma group. To gain further insight into the structure-function relations of this ribozyme, we have searched for the RNase P RNA gene from more distant relatives, the phytoplasmas. These mycoplasma-like organisms are the aetiological agents of many severe plant diseases. We report the sequence and catalytic properties of RNase P RNA from the phytoplasma causing apple proliferation disease. The primary and postulated secondary structure of this 443 nt long RNA are most similar to those of Acholeplasma, supporting the phylogenetic position of this pathogen. Remarkably, the extremely AT-rich (73.6%) phytoplasma RNA differs from the known bacterial consensus sequence by a single base pair, which is positioned close to the substrate cleavage site in current three-dimensional models. Phytoplasma RNase P RNA functions as an efficient ribozyme in vitro. Conversion of its sequence to the full consensus and kinetic analysis of the resulting mutant RNAs suggests that neither the sequence alone, nor the type of pairing at this position is crucial for substrate binding or catalysis by the RNase P ribozyme. These results refine the bacterial consensus structure close to the catalytic core and thus improve our understanding of RNase P RNA function.

Acholeplasmataceae↗
PubMed2001

In vitro and in vivo processing of cyanelle tmRNA by RNase P.

Ribonuclease P, the ubiquitous endonuclease required for generating mature tRNA 5' ends, is a ribonucleoprotein in most organisms and organelles, with the exception of mitochondria and chloroplasts of multicellular organisms. The cyanelle of the primitive alga Cyanophora paradoxa is the only photosynthetic organelle where the ribonucleoprotein nature of this enzyme has been functionally proven. tmRNA is another highly structured RNA: it can be aminoacylated with alanine, which is then incorporated into a tag peptide encoded on the same RNA molecule. This dual-function RNA has been found in bacteria, and its gene is also present in mitochondria and plastids from primitive organisms. Since nothing is known about the expression of this RNA in organelles, we have performed processing studies and determined the promoter of cyanelle pre-tmRNA. This RNA is transcribed as a precursor molecule in vivo. Synthetic transcripts of cyanelle pre-tmRNA, including or lacking the mature 3' CCA-end, are efficiently and correctly processed in vitro by bacterial RNase P ribo- and holoenzymes and by the homologous cyanelle RNase P. In addition to these experimental data, we propose a novel secondary structure model for this organellar tmRNA, which renders it more similar to its bacterial counterpart.

Base Sequence↗
PubMed2000

The DALI system.

Explore the source record for details and available documents.

Animals↗
PubMed2000

A dual function alpha-dioxygenase-peroxidase and NAD(+) oxidoreductase active enzyme from germinating pea rationalizing alpha-oxidation of fatty acids in plants.

An enzyme with fatty acid alpha-oxidation activity (49 nkat mg(-1); substrate: lauric acid) was purified from germinating pea (Pisum sativum) by a five-step procedure to apparent homogeneity. The purified protein was found to be a 230-kD oligomer with two dominant subunits, i.e. a 50-kD subunit with NAD(+) oxidoreductase activity and a 70-kD subunit, homolog to a pathogen-induced oxygenase, which in turn shows significant homology to animal cyclooxygenase. On-line liquid chromatography-electrospray ionization-tandem mass spectrometry revealed rapid alpha-oxidation of palmitic acid incubated at 0 degrees C with the purified alpha-oxidation enzyme, leading to (R)-2-hydroperoxypalmitic acid as the major product together with (R)-2-hydroxypalmitic acid, 1-pentadecanal, and pentadecanoic acid. Inherent peroxidase activity of the 70-kD fraction decreased the amount of the (R)-2-hydroperoxy product rapidly and increased the level of (R)-2-hydroxypalmitic acid. Incubations at room temperature accelerated the decline toward the chain-shortened aldehyde. With the identification of the dual function alpha-dioxygenase-peroxidase (70-kD unit) and the related NAD(+) oxidoreductase (50-kD unit) we provided novel data to rationalize all steps of the classical scheme of alpha-oxidation in plants.

Amino Acid Sequence↗
PubMed2000

Identification of a small RNA within the pdh gene cluster of Mycoplasma pneumoniae and Mycoplasma genitalium.

A highly abundant and heterogeneous small RNA about 205 to 210 bases long named MP200 RNA has been identified in Mycoplasma pneumoniae. It was localized on the genome within a 319-bp-long intergenic space of the pyruvate dehydrogenase (pdh) gene cluster. A database search at the DNA level revealed the highest similarity to a sequence located within the pdh gene cluster of Mycoplasma genitalium that was also shown to be transcribed into two abundant, but smaller RNAs than the ones in Mycoplasma pneumoniae. The RNAs from both M. pneumoniae and M. genitalium have the potential to code for cysteine-rich 29- and 23-amino-acid-long peptides, but so far, these peptides have not been identified experimentally in bacterial protein extracts.

Amino Acid Sequence↗
PubMed1999

Cyanelle RNase P: RNA structure analysis and holoenzyme properties of an organellar ribonucleoprotein enzyme.

The cyanelle of the primitive alga Cyanophora paradoxa is the only photosynthetic organelle where the ribonucleoprotein nature of ribonuclease P has been functionally proven. To increase our knowledge about RNA structure and overall composition of this enzyme, we have now determined relevant physical parameters and performed RNA accessibility experiments. Buoyant density and relative molecular mass of cyanelle RNase P were more similar to the eukaryotic (nuclear or mitochondrial) than to the bacterial enzyme type, despite the close phylogenetic relationship between plastids and cyanobacteria. Enzymatic and chemical probing was used to establish the secondary structure of cyanelle RNase P RNA. The results obtained with the naked transcript support the previously proposed, phylogenetically derived structure. Probing of the RNA in the holoenzyme resulted in reduced sensitivity at a large number of positions, indicating that these regions might be located in the interior of the ribonucleoprotein. Protection of the RNA in cyanelle RNase P was more extensive than reported for the Escherichia coli holoenzyme, but similar to the pattern observed in yeast nuclear RNase P. Taken together, these results indicate that the protein contribution in cyanelle RNase P is much larger than in the bacterial enzymes, and that the overall composition of the holoenzyme resembles that found in eukaryotes.

Base Sequence↗
PubMed1999

Ribonuclease P: the diversity of a ubiquitous RNA processing enzyme.

Ribonuclease P is the endonuclease required for generating the mature tRNA 5'-end. The ribonucleoprotein character of this enzyme has now been proven in most organisms and organelles. Exceptions, however, are still the chloroplasts, plant nuclei and animal mitochondria where no associated RNAs have been detected to date. In contrast to the known RNA subunits, which are fairly well-conserved in size and structure among diverse phylogenetic groups, the protein contribution to the holoenzyme is highly variable in size and number of the individual components. The structure of the bacterial protein component has recently been solved. In contrast, the spatial arrangement of the multiple subunits in eukaryotic enzymes is still enigmatic. Substrate requirements of the enzymes or their catalytic RNA subunits are equally diverse, ranging from simple single domain mimics to an almost intact three-dimensional structure of the pre-tRNA substrate. As an example for an intermediate in the enzyme evolution, ribonuclease P from the Cyanophora paradoxa cyanelle will be discussed in more detail. This enzyme is unique, as it combines cyanobacterial and eukaryotic features in its function, subunit composition and holoenzyme topology.

Animals↗
PubMed1998

RNase P RNA from Prochlorococcus marinus: contribution of substrate domains to recognition by a cyanobacterial ribozyme.

The molecular organisation of the Prochlorococcus marinus rnpB gene and the catalytic activity of the encoded RNA were characterised. Kinetic parameters for several pre-tRNA substrates were comparable to those from other eubacterial RNase P RNAs, although unusually high cation concentrations were required. The CCA-end of pre-tRNAs is essential for efficient turnover despite the lack of the canonical binding motif in P. marinus RNase P RNA. A trnR gene is located only 38 nt upstream the rnpB 5' end on the complementary strand. This arrangement resembles those in the plastids of Cyanophora and Porphyra but not in any other bacterium.

Base Sequence↗
PubMed1998

Sequence and functional characterization of RNase P RNA from the chl alb containing cyanobacterium Prochlorothrix hollandica.

Only a few complete sequences and very limited functional data are available for the catalytic RNA component of cyanobacterial RNase P. The RNase P RNA from the chl alb containing cyanobacterium Prochlorothrix hollandica belongs to a rarely found structural subtype with an extended P15/16 domain. We have established conditions for optimal in vitro ribozyme activity, and determined the kinetic parameters for cleavage of pre-tRNA(Tyr). Analysis of pre-tRNA mutants revealed that the T-stem sequence only plays a modulating role, whereas the CCA end is essential for efficient product formation.

Base Sequence↗
PubMed1997

A left temporal lobe impairment of auditory information processing in schizophrenia: an event-related potential study.

A measure of auditory prepulse inhibition (PPI) is the reduction of the scalp-recorded P1 event-related potential (ERP) after a sound that is preceded by 100-300 ms by a click as prepulse. This measure of sensory gating was adapted to study the effect of a prepulse on processing tones that were part of a 'go no-go' discrimination. ERPs were recorded at right and left, frontal and temporal sites in groups of patients with schizophrenia (SCH) or obsessive compulsive disorder (OCD) and healthy controls (CON). A prepulse 100 ms but not 500 ms before either tone reduced the P1 ERP amplitude in healthy and OCD subjects but not SCH patients. At frontal and temporal recording sites the P1 amplitude was similar bilaterally in controls but showed a right temporal shift in the SCH patients. If the tone was the 'no-go' tone, the prepulse reduced the N1 amplitude in both the CON and SCH groups. The N1 was similar, bilaterally in controls but again showed a right temporal shift in the SCH group. These results show a reduction of a PPI-like effect on early processing (P1) that is more marked in the left hemisphere of SCH patients and may affect channel selection for processing information (N1) about task-relevant sounds.

Acoustic Stimulation↗
PubMed1997

Endovascular AAA treatment: expensive prestige or economic alternative?

OBJECTIVES: To compare the costs of endovascular aneurysm treatment versus open surgery during the perioperative period. METHODS: Retrospective analysis of a consecutive series of 44 patients undergoing infrarenal abdominal aneurysm repair from February 1995 to March 1996 at a university teaching hospital. RESULTS: No endovascular procedure was converted to open repair. Operative time was shorter for endovascular treatment (207.6 min vs. 229.1 min, n.s.), as well as postoperative intensive care unit stay (ICU, 22.7 h vs. 55.0 h, p = 0.017) and the postoperative recovery period (5.6 days vs. 13.3 days, p < 0.001). Open surgery generated significantly more costs (25,374.07 ECU vs. 22,268.78 ECU, p < 0.001), despite evaluation and a more expensive endovascular procedure (10,699.48 ECU vs. 4032.01 ECU, p < 0.001). During the study, costs for open surgery exceeded the cost for endovascular treatment by 13.95%. CONCLUSIONS: Endovascular aneurysm treatment is cost effective and less expensive than open surgery. The main reason for cost saving is faster patient recovery after surgery, associated with a shorter LOS in the patients treated with endovascular procedure.

Aged↗
PubMed1996

RNase P from a photosynthetic organelle contains an RNA homologous to the cyanobacterial counterpart.

RNase P is a ribonucleoprotein enzyme in all organisms and organelles investigated so far, with the exception of chloroplasts where no enzyme-associated RNA has been detected to date. As an approach to answer the question whether an RNA component is present in RNase P from photosynthetic organelles, we have used a phylogenetically oriented strategy and searched for RNase P RNA in a postulated intermediate in plastid evolution, the cyanelle of Cyanophora paradoxa. We have detected a 351 nucleotide long RNA similar to cyanobacterial RNase P RNAs, with a proposed secondary structure that closely resembles a bacterial consensus. The RNA is encoded on the cyanelle genome and copurifies with enzyme activity. The RNA is not catalytically active by itself, but the activity of the cyanelle RNase P holoenzyme is destroyed by nuclease treatment, indicating an essential role of the RNA. Hence cyanelle RNase P, combining properties of bacterial and eukaryotic enzymes, occupies an intermediate position in RNA enzyme evolution. The first description of an RNA component in RNase P from a photosynthetic organelle might thus be an important step towards an understanding of plastid RNase P structure and function.

Base Sequence↗
PubMed1996

Localization and expression of the closely linked cyanelle genes for RNase P RNA and two transfer RNAs.

The genomic region encoding the RNA subunit of the cyanelle RNase P has been characterized. rnpB, which has no homologue in chloroplasts, is flanked by two tRNA genes on the complementary DNA strand. Transcriptional control elements of all three genes have been experimentally determined. Comparison of the sequenced region with the corresponding loci of chloroplast genomes from vascular plants suggests that major inversions may have led to a possible loss or severe truncation of the RNase P RNA coding region during the course of plastid evolution.

Base Sequence↗
PubMed1996

CONRAD: a method for identification of variable and conserved regions within proteins by scale-space filtering.

Advanced sequencing techniques allow rapid deduction of individual amino acid sequences of highly related proteins. Due to their quasi-species nature, viral genomes (e.g. HIV-1) represent one of the most common sources of related proteins. Another example of related proteins are immunoglobulins. Local differences in amino acid conservation are useful indicators of potential domain structures and immunological or functional epitopes prior to structural analysis of proteins. Although variability indices can be calculated by several methods, delineation of boundaries between sequence stretches with similar variability indices is left to the user. We use algorithmic scale-space filtering for delineation of conserved and variable sequence stretches within a protein which is performed on an algorithmic basis avoiding arbitrary assignments. Out method correctly identified variable regions for the human immunoglobulin lambda-chain V-regions (subgroup I). Prediction of the variable regions of the HIV-1 gp120 env protein was in agreement with empirical derived definitions. These examples indicate that our method is useful for the regional assignment of protein variability solely on the basis of amino acid sequences.

Algorithms↗
PubMed1996

Clinical evaluation of the faecal elastase test in the diagnosis and staging of chronic pancreatitis.

OBJECTIVE: To test the diagnostic accuracy of faecal elastase (FE), a new test of exocrine pancreatic function, in a large prospective population of patients with abdominal complaints. METHODS: Between January 1994 and December 1995, 131 patients (age range 17-82 years) were submitted for exocrine pancreatic function testing. Sixty-three patients had a firm diagnosis of chronic pancreatitis (CP) at stage I-III according to endoscopic retrograde cholangiopancreatography (ERCP). Twenty patients suffered from other pancreatic diseases (PD), and 48 patients had various other gastrointestinal diseases (GD). Fifty-seven healthy controls (HC) were also investigated. Stool specimens were analysed for FE by enzyme-linked immunosorbent assay (ELISA) and for faecal chymotrypsin (FC). The pancreolauryl serum test (PLT) was also performed in 97 patients and 23 healthy controls. RESULTS: FE was 200; 45-500 micrograms/g (median; range) in CP-I (n = 19), 94; 0-400 micrograms/g in CP-II (n = 14) and 38; 0-135 micrograms/g in CP-III patients (n = 30). With a cutoff of 200 micrograms/g, abnormal test results were found in 47% of CP-I, 79% of CP-II and 100% of CP-III patients; in 30% of PD patients, in 38% of GD patients and in 7% of HC. Sensitivity of abnormal FE in diagnosing CP was 79% (FC: 48%; PLT: 71%). The specificity of only 62% (FC: 73%; PLT: 67%) in the GD group increased to 78% (FC: 81%; PLT: 77%) when patients with small bowel diseases and diarrhoea (n = 22) were excluded. CONCLUSION: Faecal elastase is more sensitive than chymotrypsin and comparable to the pancreolauryl test in the diagnosis of chronic pancreatitis. Indirect exocrine pancreatic function tests are not helpful to differentiate between pancreatic and small bowel diseases in a prospective population of patients with abdominal complaints.

Adolescent↗
PubMed1996

Event-related potentials during an auditory discrimination with prepulse inhibition in patients with schizophrenia, obsessive-compulsive disorder and healthy subjects.

Prepulse inhibition (PPI) is a measure of the influence of a stimulus (S1) on the response elicited by a second stimulus (S2) occurring shortly afterwards. Most S1/S2 measures of gating have used behavioural startle and the P50 event-related potential (ERP) amplitudes to detect PPI in a simple paired stimulus paradigm. We report on two behavioural (reaction time, RT, and the electromyographically recorded response of the musculus orbicularis oculi, EMG) and 5 ERP measures of PPI where S2 was the target in an auditory two-tone discrimination. Subjects were 21 healthy controls (CON), 11 obsessive-compulsive (OCD) and 9 schizophrenic patients (SCH). The prepulse 100 ms before S2 induced more omission errors and longer RTs compared to 500ms S1-S2 interval in all subjects. PPI was also evident in EMG, P50, N1, P3 but not P2 or N2 amplitudes of CON subjects. SCH patients showed attenuation of PPI on the same measures. OCD patients were characterized only by their slow RT and a marginal attenuation of PPI of the EMG response. A correlational analysis implied separate relationships of ERP indices of PPI to the cognitive and psychomotor consequences of the prepulse on behavioural and discrimination responses. However, SCH patients showed a general rather than a specific impairment of these indices.

Acoustic Stimulation↗