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Biomedical subjects

A Falk

Publications and source records attributed to A Falk.

At least 19 recordsLinked to original sources
PubMed1999

EDS1, an essential component of R gene-mediated disease resistance in Arabidopsis has homology to eukaryotic lipases.

A major class of plant disease resistance (R) genes encodes leucine-rich-repeat proteins that possess a nucleotide binding site and amino-terminal similarity to the cytoplasmic domains of the Drosophila Toll and human IL-1 receptors. In Arabidopsis thaliana, EDS1 is indispensable for the function of these R genes. The EDS1 gene was cloned by targeted transposon tagging and found to encode a protein that has similarity in its amino-terminal portion to the catalytic site of eukaryotic lipases. Thus, hydrolase activity, possibly on a lipid-based substrate, is anticipated to be central to EDS1 function. The predicted EDS1 carboxyl terminus has no significant sequence homologies, although analysis of eight defective eds1 alleles reveals it to be essential for EDS1 function. Two plant defense pathways have been defined previously that depend on salicylic acid, a phenolic compound, or jasmonic acid, a lipid-derived molecule. We examined the expression of EDS1 mRNA and marker mRNAs (PR1 and PDF1.2, respectively) for these two pathways in wild-type and eds1 mutant plants after different challenges. The results suggest that EDS1 functions upstream of salicylic acid-dependent PR1 mRNA accumulation and is not required for jasmonic acid-induced PDF1.2 mRNA expression.

Amino Acid Sequence↗
PubMed1999

Effects of collimator size of a dental X-ray unit on image contrast.

OBJECTIVES: To examine the effect of collimator size on image contrast in dental radiography. METHODS: Two conventional collimators, one circular (53 mm in diameter) and one rectangular (35x45 mm2), were compared with a small rectangular collimator (26x39 mm2). Low-contrast and high-contrast resolution was assessed with the aid of contrast-detail and line-pair phantoms. RESULTS: Shallower holes were observed with the small rectangular collimator. Two-thirds of 17 observers assessing high-contrast resolution considered the small collimator to result in a clearer image than the conventional collimators. The same effect was demonstrated with the line-pair phantom and by microdensitometry. With the small collimator the energy imparted is estimated to be reduced by 54 and 36% compared with the conventional circular and rectangular collimators respectively. CONCLUSIONS: Decrease of the collimator size to fit the film size used for children will result in improved low-contrast and, under some conditions, improved high-contrast resolution. This improvement might have implications for caries diagnosis and monitoring.

Absorptiometry, Photon↗
PubMed1999

Clinical utility of magnetic resonance angiography in the evaluation of aneurysms from a neurosurgical point of view.

The possibilities and limitations of MRA in the evaluation of intracranial aneurysms were investigated in this study. 54 patients, 30 with acute SAH were diagnosed using the three dimensional time-of-flight MRA in comparison with a conventional four vessel digital subtraction angiography prior to surgery. Furthermore, postoperative MRA was performed to assess clip placement and vessel patency and to search for innocent additional aneurysms in patients with emergency surgery due to intracerebral hemorrhage causing mass effect in whom preoperatively only the side of the lesion was investigated in DSA. 64 aneurysms in all vessel territories were detected. Three aneurysms were missed in MRA and there were three false positive results. Four baby-aneurysms were missed by both imaging modalities and were found during surgery. In all patients with CT scans suspicious of aneurysms MRA was able to detect or rule out the aneurysm. Postoperative MRA to demonstrate clip placement and vessel patency was not possible due to susceptibility artefacts. MRA should be the diagnostic procedure of first choice in CT findings suspicious of aneurysms. The follow-up of confirmed aneurysms is safely possible. MRA is very well applicable in the acute setting after SAH. The axial acquisition films and the rotatable maximum intensity projection reconstructions provide useful insights into the location of the aneurysm and its neighboring structures thus influencing the preoperative planning of surgical strategies. Keeping the limitations in mind it is a safe tool in the evaluation of aneurysms, especially with the rapidly improving postoprocessing possibilities.

Adolescent↗
PubMed1998

Preoperative planning and intraoperative navigation: status quo and perspectives.

An essential step in modern microneurosurgery involves preoperative planning of procedures. For difficult lesions neuronavigation is being used in conjunction with complex and detailed radiological investigations. This article shows how these examinations are used for computerized planning of surgical steps. Although planning and navigation are still two separate entities, the combination of the two may help in neurosurgery.

Aged↗
PubMed1998

Operative approach due to results of functional magnetic resonance imaging in central brain tumors.

Since 1995 we have been investigating the localization of the cortical motor strip by functional magnetic resonance imaging (fMRI) in central brain tumor cases. Forty patients have been operated on using these data for preoperative planning. Intraoperative sensory evoked potentials (SEP) and cortical motor evoked potential (performed in 18 patients) showed a good correlation with fMRI data with the exception of two cases. Only 12.5% of cases were permanently worsened as a result of increasing postoperative pareses.

Brain Neoplasms↗
PubMed1998

Change in size, number and morphology of the nucleoli in human hearts as a result of hyperfunction.

In the present study we examined light-microscopically the nuclei of 16 hearts (7 normal hearts, 7 hearts with hypertrophy and 2 hearts with atrophy) for the size, number and morphology of their nucleoli. The size of the nucleoli, defined as the total area of all nucleoli per nucleus, was an early and sensitive indication of a beginning hypertrophy of the myocardium. It increased in parallel to the total heart weight and to the total area of the nucleus of the cell, but initially the size of the nucleoli changed earlier than the other parameters. We found an increase of the ratio in the total area of the nucleoli per nucleus to the total area of the nucleus at the beginning of clinical hyperfunction. This ratio normalised during chronic hyperfunction. The number of the nucleoli also increased during hyperfunction, but it did not exceed the number of nucleolus organiser regions (NOR) given by the number of chromosomes. Nevertheless, we found numbers of nucleoli higher than 10 because, the number of NORs increases during polyploidization. Regarding the morphology of the nucleoli in hearts with hypertrophy, we found a predomination of the nucleoli with a highly branched nucleolonemal structure as an indication of an increased RNA synthesis.

Atrophy↗
PubMed1998

Patency of Wallstents placed across the venous anastomosis of hemodialysis grafts after percutaneous recanalization.

PURPOSE: To determine the patency of Wallstents placed across the venous anastomosis of prosthetic bridge grafts after percutaneous graft recanalization. MATERIALS AND METHODS: Wallstents were placed across 26 lesions at the venous anastomosis of polytetrafluoroethylene (PTFE) grafts in 25 patients (11 men, 14 women; age range, 29-83 years; mean age, 65.4 years) after pulse-spray pharmacomechanical thrombolysis. Indications for stent deployment included acute angioplasty failure, rapid restenosis, and vessel perforation. RESULTS: The initial success rate was 100%. The mean primary graft patency rates (+/- standard error) at 3 and 6 months were 34% +/- 9 and 27% +/- 9, respectively. Secondary patency rates were 77% +/- 8 at 3 months, 72% +/- 9 at 6 months, and 50% +/- 10 at 12 months. Eight of the 26 grafts continued to be used for hemodialysis at the end of follow-up. CONCLUSION: After angioplasty failure or vessel perforation, Wallstent placement at the venous anastomosis of recanalized PTFE grafts can salvage hemodialysis access function. The results of this study indicate that the 1-year secondary patency rate of these grafts is 50%, which approaches the reported rates of patency after balloon dilation as part of percutaneous graft recanalization.

Aged↗
PubMed1997

Myrosinase-binding proteins are derived from a large wound-inducible and repetitive transcript.

Several non-myrosinase proteins have been found in association with some of the myrosinases extracted from rape (Brassica napus) seed. Most of these proteins seemed to belong to a large family of proteins ranging in size over approximately 30-110 kDa, namely the myrosinase-binding protein (MBP) family. Potentially all of these MBPs might be derived from a single large precursor, encoded by a 3.3-kb transcript. This transcript coded for a 99-kDa glycine-rich protein with a highly repetitive structure. The mature 50-kDa and 52-kDa MBP amino-terminal was located 255 amino acids from the putative initiation methionine. Also, a more divergently related transcript, the protein product of which was unknown, has been cloned. However, the largest open reading frame suggested a proline-rich protein. While this transcript seemed to be expressed predominantly in seeds, the MBP transcripts were expressed in several tissues and also exhibited a responsiveness to wounding and methyl jasmonate. Both proteins exhibited significant similarities to lectins from Artocarpus integer and from Maclura pomifera.

Amino Acid Sequence↗
PubMed1997

Continuous intravenous infusion of omeprazole in elderly patients with peptic ulcer bleeding. Results of a placebo-controlled multicenter study.

BACKGROUND: Does profound acid inhibition by continuous infusion of omeprazole for 72 h reduce further bleeding in elderly patients with peptic ulcer bleeding (PUB)? METHODS: Three hundred and thirty-three patients > or = 60 years old with PUB were randomized to omeprazole (80 mg + mg/h) or placebo as continuous infusion for 72 h. From day 4 to 21 all patients received 20 mg omeprazole orally once daily. RESULTS: When evaluated on day 3, the primary variable 'overall outcome' (based on an ordinal ranking scale; see Study variables) (P = 0.017) and the secondary variables, surgery (P = 0.003), degree (P = 0.004) and duration of bleeding (P = 0.003) all favored the omeprazole group. Blood transfusions, need for endoscopic treatment, and mortality were not statistically different. On follow-up, by day 21, the mortality in the group initially receiving intravenous omeprazole was 6.9%, while the intravenous placebo group showed an extremely low mortality, 0.6%. CONCLUSION: Three days' infusion of omeprazole improved overall outcome and reduced need for intervention in PUB patients.

Aged↗
PubMed1997

Virtual reality in surgical practice in vitro and in vivo evaluations.

This paper describes a method for the acquisition and integrative processing of laparoscopic and endoluminal ultrasound images. We used a stepping motor attached to a stabilizing rig, interfaced to the laparoscope, or the ultrasound probe. 360 degrees laparoscopic scenes were constructed during minimally invasive surgery, and three-dimensional reconstructions were made of related ultrasound data. Integration of 360 degrees panoramas with geometric ultrasound models could be displayed as interactive scenes. This resulted in a better demonstration of the surgical field and topographic anatomy. In conclusion, this type of visualizations may be used in virtual reality simulations for documentation, education and in operative planning.

Computer Simulation↗
PubMed1996

[3-D-TONE magnetic resonance angiography in the detection of intracranial aneurysms compared with digital subtraction angiography. A prospective study].

PURPOSE: To evaluate the efficiency and accuracy of the optimized 3-D-MT-TONE-magnetic resonance angiography (MRA) with that of intraarterial digital subtraction angiography (DSA) in the detection of intracranial aneurysms. MATERIAL AND METHODS: From March 1994 to March 1995 30 patients with 38 aneurysms were prospectively subjected to MRA as well as to DSA. Respiratory insufficient patients were excluded from MRA. RESULTS: The aneurysm size ranged from 3-50 mm with an average size of 9 mm. Correct diagnosis was done in 33 aneurysms (86.8%) in 26 of the patients. In 4 patients (13.3%) with 5 aneurysms, the blinded readers made an incorrect diagnosis due to degradation of image quality. One (2.6%) aneurysm was falsely described via MRA as well as via DSA. The sensitivity was 86.8%. In the control group of 30 patients three aneurysms were found, therefore the specificity was 90% and we could calculate a positive predictive value of 97.1%, a negative predictive value of 84.4% and a correct diagnosis of 90.1%. CONCLUSION: Our results show that MT-TONE-MRA is a useful non-invasive technique with improved vascular detail and vascular background for detection of intracranial aneurysm. Further technical improvements are necessary for better visualisation of pathological findings in the carotid siphon, where only 60% of the aneurysms could be clearly detected.

Adult↗
PubMed1996

A wound- and methyl jasmonate-inducible transcript coding for a myrosinase-associated protein with similarities to an early nodulin.

Myrosinase is regarded as a defense-related enzyme in the Brassicaceae and is capable of hydrolyzing glucosinolates into various compounds, some of which are toxic. Several myrosinase isoenzymes exist, and some of them have been found in association with nonmyrosinase proteins. One of these associated proteins, myrosinase-associated protein (MyAP), was purified from seeds of Brassica napus both in complexes with myrosinase and in a free form. MyAP is a glycosylated, 40-kD protein with at least one intramolecular disufide bridge. A monoclonal anti-MyAP antibody precipitated myrosinase activity from B. napus seed extracts and in these complexes both a 65- and a 70-kD myrosinase were present. The subsequent cloning and analysis revealed the existence of a gene family encoding MyAP or MyAP-related protein and that transcripts corresponding to MyAP in nonwounded plants are found predominantly in seeds. At least some members of the gene family exhibited responsiveness toward wounding and methyl jasmonate vapor. MyAP displayed considerable similarity to an early nodulin (ENOD8) from Medicago sativa and to a proline-rich protein (APG), described as another specific, from Arabidopsis thaliana and B. napus. Similarity to expressed sequence tags from both A. thaliana and Oryza sativa has also been found.

Acetates↗
PubMed1996

Characterization of eds1, a mutation in Arabidopsis suppressing resistance to Peronospora parasitica specified by several different RPP genes.

The interaction between Arabidopsis and the biotrophic oomycete Peronospora parasitica (downy mildew) provides an attractive model pathosystem to identify molecular components of the host that are required for genotype-specific recognition of the parasite. These components are the so-called RPP genes (for resistance to P. parasitica). Mutational analysis of the ecotype Wassilewskija (Ws-0) revealed an RPP-nonspecific locus called EDS1 (for enhanced disease susceptibility) that is required for the function of RPP genes on chromosomes 3 (RPP1/RPP14 and RPP10) and 4 (RPP12). Genetic analyses demonstrated that the eds1 mutation is recessive and is not a defective allele of any known RPP gene, mapping to the bottom arm of chromosome 3 (approximately 13 centimorgans below RPP1/RPP14). Phenotypically, the Ws-eds1 mutant seedlings supported heavy sporulation by P. parasitica isolates that are each diagnostic for one of the RPP genes in wild-type Ws-0; none of the isolates is capable of sporulating on wild-type Ws-0. Ws-eds1 seedlings exhibited enhanced susceptibility to some P. parasitica isolates when compared with a compatible wild-type ecotype, Columbia, and the eds1 parental ecotype, Ws-0. This was observed as earlier initiation of sporulation and elevated production of conidiosporangia. Surprisingly, cotyledons of Ws-eds1 also supported low sporulation by five isolates of P. parasitica from Brassica oleracea. These isolates were unable to sporulate on > 100 ecotypes of Arabidopsis, including wild-type Ws-0. An isolate of Albugo candida (white blister) from B. oleracea also sporulated on Ws-eds1, but the mutant exhibited no alteration in phenotype when inoculated with several oomycete isolates from other host species. The bacterial resistance gene RPM1, conferring specific recognition of the avirulence gene avrB from Pseudomonas syringae pv glycinea, was not compromised in Ws-eds1 plants. The mutant also retained full responsiveness to the chemical inducer of systemic acquired resistance, 2,6-dichloroisonicotinic acid; Ws-eds1 seedlings treated with 2,6-dichloroisonicotinic acid became resistant to the Ws-0-compatible and Ws-0-incompatible P. parasitica isolates Emwa1 and Noco2, respectively. In summary, the EDS1 gene appears to be a necessary component of the resistance response specified by several RPP genes and is likely to function upstream from the convergence of disease resistance pathways in Arabidopsis.

Arabidopsis↗
PubMed1996

Biapenem versus imipenem/cilastatin in the treatment of complicated intra-abdominal infections: report from a Swedish Study Group.

118 patients with complicated intra-abdominal infections participated in an open randomized comparative multicenter trial in order to compare the clinical and microbiological efficacy and safety of biapenem with imipenem/cilastatin (Tienam). 31 men and 27 women (mean age 52.3 years) were enrolled in the biapenem group, and 43 men and 17 women (mean age 52.3 years) in the imipenem/cilastatin group. The patients received either biapenem 500 mg every 8 h or imipenem/cilastatin 500 mg/500 mg every 6 h by intravenous infusion for up to 13 days (mean 6.5 days). 28/43 evaluable patients (65.1%) receiving biapenem and 27/40 evaluable patients (67.5%) in the imipenem/cilastatin group were clinically cured. The microbiological response was satisfactory in 28/43 evaluable patients (65.1%) receiving biapenem and in 27/40 evaluable patients (67.5%) receiving imipenem/cilastatin. No significant differences in clinical or microbiological efficacy between the two treatment groups were found. The present study shows that biapenem may be useful in the treatment of intra-abdominal infections.

APACHE↗
PubMed1995

Characterization of a new myrosinase in Brassica napus.

A full-length cDNA clone defining the new myrosinase gene family MC in Brassica napus was isolated and sequenced. Southern hybridization showed that the MC family probably consists of 3 or 4 genes in B. napus. MC genes are expressed in the developing seed, but not in the vegetative tissues investigated. In situ hybridizations to developing seeds showed that the MC genes are expressed in the myrosin cells of the embryo axis and the cotyledons. Complexes with myrosinase and myrosinase-binding protein (MBP) were purified and characterized. Sequencing of peptides from myrosinases occurring in the complexes showed that the 70 kDa myrosinase is encoded by the MC genes, whereas the 65 kDa myrosinase is encoded by the MB genes. This is in contrast to the 75 kDa myrosinase which occurs in free form and is encoded by the MA genes. Deglycosylations of the myrosinase complexes and the free myrosinase showed that the molecular sizes of the myrosinases could be reduced significantly by this treatment, and that the size differences between the different myrosinases are mainly due to differences in glycosylation.

Amino Acid Sequence↗