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PubMed2000

MR CAT scan: a modular approach for hybrid imaging.

In this study, a modular concept for NMR hybrid imaging is presented. This concept essentially integrates different imaging modules in a sequential fashion and is therefore called CAT (combined acquisition technique). CAT is not a single specific measurement sequence, but rather a sequence design concept whereby distinct acquisition techniques with varying imaging parameters are employed in rapid succession in order to cover k-space. The power of the CAT approach is that it provides a high flexibility toward the acquisition optimization with respect to the available imaging time and the desired image quality. Important CAT sequence optimization steps include the appropriate choice of the k-space coverage ratio and the application of mixed bandwidth technology. Details of both the CAT methodology and possible CAT acquisition strategies, such as FLASH/EPI-, RARE/EPI- and FLASH/BURST-CAT are provided. Examples from imaging experiments in phantoms and healthy volunteers including mixed bandwidth acquisitions are provided to demonstrate the feasibility of the proposed CAT concept.

Abdomen↗

PubMed1994

Auditory-visual spatial interaction and modularity

The results of dealing with the conditions for pairing visual and auditory data coming from spatially separate locations argue for cognitive impenetrability and computational autonomy, the pairing rules being the Gestalt principles of common fate and proximity. Other data provide evidence for pairing with several properties of modular functioning. Arguments for domain specificity are inferred from comparison with audio-visual speech. Suggestion of innate specification can be found in developmental data indicating that the grouping of visual and auditory signals is supported very early in life by the same principles that operate in adults. Support for a specific neural architecture comes from neurophysiological studies of the bimodal (auditory-visual) neurons of the cat superior colliculus. Auditory-visual pairing thus seems to present the four main properties of the Fodorian module.

Adaptation, Physiological↗

PubMed2000

Controlled expression of tagged proteins in Drosophila using a new modular P-element vector system.

We have developed a new modular vector system that facilitates the combination of various DNA fragments as functional modules for P element-mediated transformation of Drosophila melanogaster. The basic vector pP¿GS¿ contains unique sites for 17 restriction enzymes, including three 8-bp cutters, that allow one to combine various promoter elements, cDNAs and genomic DNA fragments, as well as protein tags and selectable marker genes, for a wide spectrum of transgene analyses. With this new vector system we analysed the chromosomal distribution of the Drosophila SU(VAR)3-9 protein tagged with EGFP, using hsp70-cDNA and genomic Su(var)3-9 constructs. We found preferential association of the tagged SU(VAR)3-9 with centric heterochromatin.

Animals↗

PubMed2001

[Changes in bone density of the femur after cement-free implantation of a modular hip prosthesis with a long shaft].

Until now, no reports exist on the existence of femoral bone loss after hip arthroplasty using long-stem cementless prostheses in elderly patients. In a prospective evaluation the amount of bone loss (stress-shielding) after implantation of a long stem hip prosthesis in patients with femoral neck fractures (group A) or pertrochanteric femoral fractures (group B) was examined. Eleven patients (five from group A and six from group B) were treated with a long-stem modular hip prosthesis (MHP). Change of bone mass was evaluated using quantitative computed tomographie (QCT) immediately following and at six months (group A and B) and twelve months (group A) after implantation of the prosthesis. Clinical results, expressed with the modified Harris Hip Score, and relative changes of bone mass were compared with mean periprosthetic bone mass of the femur after operation. After implantation of the MHP, the maximum decrease of mean femoral bone mass was 19.1% at six months and 20.2% at twelve months for group A and 29.5% at six months for group B. Bone loss in the proximal periprosthetic area was higher than in the distal part. There was no correlation between baseline values of bone mass and the amount of stress-shielding or clinical outcome.

Aged↗

PubMed1999

[Quality of life. Construct validation and the development of a modular system].

The construct Quality of Life (QoL) is investigated by metaanalysis of eight (inter)nationally validated questionnaires in a multicenter study. Data have been collected in a mentally healthy (n = 479), a depressed (n = 171) and a schizophrenic (n = 139) sample. Conventional psychometric criteria and a facet analytical methodology have been applied. The resulting questionnaire "Modular System for Quality of Life" (MSQoL) consists of a core module with 47 items (one "G-factor" and six subdimensions), which is sufficiently valid for all three samples. Additionally, there are four specific modules (demography, family, partnership, profession). No specific modules can be identified for the psychopathological subgroups. The validated radex structure for subjective QoL offers the opportunity for a cumulative research design and for adaptations to the actual setting.

Adolescent↗

PubMed2001

Modular organization of the monkey presubiculum.

There have been previous reports of somatostatin- and acetylcholinesterase (AChE)-positive patches in the superficial layers of the presubiculum in monkeys. In this study, we show additional instances of patches in the presubiculum, as demonstrated by cytochrome oxidase (CO), by myelin and Nissl stains, and by the calcium-binding proteins calbindin (CB), calretinin (CR), and parvalbumin (PV). Markers are differentially expressed along the lateral and longitudinal axes. Comparisons of adjacent sections reacted for different markers suggest that the CB+ and CR+ patches, and CO+ and AChE+ patches generally correspond, but not the CB+ and CO+ patches. In cross section, patches are about 100-300 microm in width. Sections cut tangentially through the superficial layers indicate that the pattern of CO and AChE labeling is in fact patchlike in layer I, but that the apparent patches in layer II (CB and CR) form a reticular or lattice-like network. As patches are restricted to the presubiculum, these labeling patterns provide a convenient marker for the boundary between the presubiculum and the adjoining posteroventral retrosplenial cortex. More work is necessary to determine how this modularity may relate to the functional organization of the presubiculum.

Acetylcholinesterase↗

PubMed1996

Do the non-catalytic polysaccharide-binding domains and linker regions enhance the biobleaching properties of modular xylanases?

Xylanase A (XylA) from Pseudomonas fluorescens subsp. cellulosa consists of an N-terminal non-catalytic cellulose-binding domain joined to a functionally independent C-terminal catalytic domain by a sequence rich in serine residues. Xylanase D (XylD) from Cellulomonas fimi also exhibits a modular structure comprising an N-terminal catalytic domain linked to an internal non-catalytic xylan-binding domain and a C-terminal cellulose-binding domain. To determine the importance of the non-catalytic polysaccharide-binding domains and linker sequences of XylA and XylD in relation to their capacity to hydrolyse pulp xylan and enhance bleachability, purified full-length and modified derivatives of both enzymes were incubated with a hardwood kraft pulp. Deletion of the cellulose-binding domain or linker region from XylA decreased the activity of the enzyme against pulp xylan, but had no significant effect on the capacity of the enzyme to facilitate delignification and reduce pulp kappa number. While full-length and truncated forms of XylD, lacking either the cellulose-binding or the cellulose- and xylan-binding domains, were equally effective in hydrolysing pulp xylan, enzyme derivatives containing a polysaccharide-binding domain were marginally more efficient in reducing pulp kappa number. The reduction in kappa number elicited by full-length and isolated catalytic domains of XylA and XylD was reflected in an increase in the brightness of paper handsheets derived from pretreated pulps. Thus, the polysaccharide-binding domains of XylA and XylD did not appear to confer any advantage in terms of the ability of the enzymes to improve pulp bleachability. However, XylA and XylD, which belong to different glycosyl hydrolase families, differed in their ability to hydrolyse pulp xylan and facilitate the delignification of kraft pulp.

Actinomycetales↗

PubMed2000

A modular femoral implant for uncemented stem revision in THR.

We present the early results of 142 uncemented femoral stem revisions using the modular MRP-Titan system. There were 70 cases with marked preoperative femoral bone defects (Paprosky type 2C and type 3); and bone grafts were used in 31 cases. At a mean follow-up of 2.3 years five cases were re-revised due to dislocation and two due to aseptic loosening. The mean Harris hip score improved from 37.4 preoperatively to 92.4. In 122 cases progressive bone regeneration on X-ray was seen; and no further osteolysis was observed.

Adult↗

PubMed2000

Limb salvage for proximal tibial tumours using a modular prosthesis.

We report early results after the resection of proximal tibial tumours followed by reconstruction using a modular prosthesis. The indication for wide resection was a malignant tumour in 13 patients, and a neglected giant cell tumour in 2. There were no mechanical failures during an average follow-up of 3.5 years. However, there were 5 peroneal nerve palsies, 1 complete sciatic nerve palsy, 1 vascular injury leading to an above knee amputation, and 2 deep prosthetic infections. There were 2 superficial skin necroses and 1 fracture proximal to the femoral prosthetic component. The mean post-operative Musculo-Skeletal Tumour Society (MSTS) score in 12 patients who still had their prosthesis in situ was 18.3 out of a possible total of 30 (range: 10-28). Limb salvage surgery in the proximal tibia has a high early complication rate even with the use of modern implants and improved techniques.

Adolescent↗

PubMed1998

[Modular memory training for elderly adults: concept and evaluation].

We present a modular concept of a cognitive training relevant to the demands of everyday life of community dwelling older adults. The concept has three major advantages. First, it takes into account the current performance levels and needs of the trainees. Second, the training is economical in aiming at selecting the most effective training elements. Third, the concept allows the evaluation of single elements of the training. The application of this concept points at the importance of training content being relevant to trainees' everyday lives. Results indicate that training effectiveness depends on the starting level of performance and the cognitive domain being trained. Overall, the results demonstrate the possibility to maximize training gains of older adults by designing adequate trainings for well-defined subgroups of normal older adults.

Activities of Daily Living↗

PubMed2000

Quality of life in psychiatry: a systematic contribution to construct validation and the development of the integrative assessment tool "modular system for quality of life".

The aim of the present study is to contribute to an ongoing validation process of the Quality of Life (QoL) construct in the clinical field by investigating its internal structure. Eight (inter)nationally validated questionnaires have been analyzed by an integrative approach in a multicenter study. Data has been collected in a mentally healthy (n = 479), a depressed (n = 171) and a schizophrenic (n = 139) sample. Apart from conventional psychometric criteria a similarity structure analysis (SSA) within a facet analytic methodology has been applied. A dimensional structure of the resulting integrative questionnaire "Modular System for Quality of Life" (MSQoL) could be generated that consists of one "G-factor" (life in general) and six specific dimensions (physical health, vitality, psychosocial relationships, material resources, affect, leisure time). This basic structure represents a core module measured by 47 items which is sufficiently valid for all three samples. The empirical structures of healthy, depressed and schizophrenic samples fulfill the first law of attitude and share a common variance of 95%. In addition, there are four specific modules (demography, family, partnership, profession). No specific modules could be identified for the psychopathological subgroups. The conclusion can be drawn that QoL is construed very similar by all three investigated populations which is the base for searching for quantitative differences and profiles. The MSQoL integrates the non-redundant components of eight QoL-instruments, is psychometrically able to assess the basic structure and can be completed within a cumulative research design by items specific for a particular setting.

Adolescent↗

PubMed1999

Emergence of symmetric, modular, and reciprocal connections in recurrent networks with Hebbian learning.

While learning and development are well characterized in feedforward networks, these features are more difficult to analyze in recurrent networks due to the increased complexity of dual dynamics - the rapid dynamics arising from activation states and the slow dynamics arising from learning or developmental plasticity. We present analytical and numerical results that consider dual dynamics in a recurrent network undergoing Hebbian learning with either constant weight decay or weight normalization. Starting from initially random connections, the recurrent network develops symmetric or near-symmetric connections through Hebbian learning. Reciprocity and modularity arise naturally through correlations in the activation states. Additionally, weight normalization may be better than constant weight decay for the development of multiple attractor states that allow a diverse representation of the inputs. These results suggest a natural mechanism by which synaptic plasticity in recurrent networks such as cortical and brainstem premotor circuits could enhance neural computation and the generation of motor programs.

Animals↗

PubMed1999

Artificial disc replacement with the modular type SB Charité III: 2-year results in 50 prospectively studied patients.

The Modular Type SB Charite disc prosthesis has been developed as a device for artificial disc replacement (ADR) in patients with symptomatic discopathies. Here, we report on our first series of 50 (out of 350) patients, who had a satisfactory clinical result in 70% of cases (2 years' follow-up). Subgroup analysis revealed that patients with an isolated discopathy without previous spinal operations or other pathology at the same or other spinal level benefitted more from the surgery. However, this technique was associated with some problems: a 13% rate of permanent side-effects and/or complications was observed caused by the anterior approach. Four percent were related to poor implantation technique. There were no problems related to the material of the prosthesis. Twelve patients needed re-operation, but this was beneficial in only three of them. In one patient we had to convert to an interbody fusion. We conclude that in patients with severe isolated symptomatic discopathies that are resistant to conservative treatment, a mobile disc prosthesis is worth considering as a real alternative to a spondylodesis. However, accurate patient selection is imperative. With these criteria we were encouraged by our results to continue the implantation of this artificial disc.

Adult↗

PubMed2000

Modular organization and identification of a mononuclear iron-binding site within the NifU protein.

The NifS and NifU nitrogen fixation-specific gene products are required for the full activation of both the Fe-protein and MoFe-protein of nitrogenase from Azotobacter vinelandii. Because the two nitrogenase component proteins both require the assembly of [Fe-S]-containing clusters for their activation, it has been suggested that NifS and NifU could have complementary functions in the mobilization of sulfur and iron necessary for nitrogenase-specific [Fe-S] cluster assembly. The NifS protein has been shown to have cysteine desulfurase activity and can be used to supply sulfide for the in vitro catalytic formation of [Fe-S] clusters. The NifU protein was previously purified and shown to be a homodimer with a [2Fe-2S] cluster in each subunit. In the present work, primary sequence comparisons, amino acid substitution experiments, and optical and resonance Raman spectroscopic characterization of recombinantly produced NifU and NifU fragments are used to show that NifU has a modular structure. One module is contained in approximately the N-terminal third of NifU and is shown to provide a labile rubredoxin-like ferric-binding site. Cysteine residues Cys35, Cys62, and Cys106 are necessary for binding iron in the rubredoxin-like mode and visible extinction coefficients indicate that up to one ferric ion can be bound per NifU monomer. The second module is contained in approximately the C-terminal half of NifU and provides the [2Fe-2S] cluster-binding site. Cysteine residues Cys137, Cys139, Cys172, and Cys175 provide ligands to the [2Fe-2S] cluster. The cysteines involved in ligating the mononuclear Fe in the rubredoxin-like site and those that provide the [2Fe-2S] cluster ligands are all required for the full physiological function of NifU. The only two other cysteines contained within NifU, Cys272 and Cys275, are not necessary for iron binding at either site, nor are they required for the full physiological function of NifU. The results provide the basis for a model where iron bound in labile rubredoxin-like sites within NifU is used for [Fe-S] cluster formation. The [2Fe-2S] clusters contained within NifU are proposed to have a redox function involving the release of Fe from bacterioferritin and/or the release of Fe or an [Fe-S] cluster precursor from the rubredoxin-like binding site.

Amino Acid Sequence↗

PubMed1983

A modular program for analysis of electrophysiological data on a laboratory minicomputer.

In the study of electrophysiological phenomena, the signals to be investigated are often reduced to sampled time series or point processes. Nowadays, the measuring equipment frequently includes one or more micro- and/or minicomputers which perform the data acquisition (including, e.g., A-D conversion and interval measurements) and the subsequent data processing and analysis. This paper describes the structured organization of data measurement and analysis of electrophysiological data performed by a modular software program implemented on a laboratory minicomputer. The program is used in our clinical laboratory by a number of research teams with different experimental objectives. The input data structure for the program has a standardized format, comprising multiplexed data channels preceded by a 256 entry parameter block containing general processing information and specific information concerning the analyses performed. The tasks carried out by the program are the calculation of distributions and correlations, digital filtering and estimation of spectra. The program can easily be extended by writing new software modules.

Computers↗

PubMed1992

The modular architecture of vertebrate collagens.

Collagens are typical mosaic proteins containing a number of shuffled domains. These domains have been classified by sequence similarity in order to characterize their structural and functional relationships to other proteins. This analysis provides an overview of homologies of collagen domains. It also reveals two new relationships: (i) a module common to type V, IX, XI, and XII collagens was found to be homologous to the heparin binding domain of thrombospondin; (ii) the modular architecture of a human type VII collagen fragment was identified. Its N-terminal globular domain contains fibronectin type III repeats located adjacent to a Von Willebrand factor type A module. The proposed structural similarities point to analogous subfunctions of the respective domains in otherwise distinct proteins.

Amino Acid Sequence↗

PubMed1995

Divergent sequence motifs correlated with the substrate specificity of (methyl)malonyl-CoA:acyl carrier protein transacylase domains in modular polyketide synthases.

The amino acid sequences of a large number of polyketide synthase domains that catalyse the transacylation of either methylmalonyl-CoA or malonyl-CoA onto acyl carrier protein (ACP) have been compared. Regions were identified in which the acyltransferase sequences diverged according to whether they were specific for malonyl-CoA or methylmalonyl-CoA. These differences are sufficiently clear to allow unambiguous assignment of newly-sequenced acyltransferase domains in modular polyketide synthases. Comparison with the recently-determined structure of the malonyltransferase from Escherichia coli fatty acid synthase showed that the divergent region thus identified lies near the acyltransferase active site, though not close enough to make direct contact with bound substrate.

Acyl Carrier Protein↗

PubMed1995

In vitro production of monoclonal antibodies in high concentration in a new and easy to handle modular minifermenter.

This paper describes a new and easy to handle reusable minifermenter for high-density culture of hybridoma and other cells. The culture apparatus is composed of two modules: a 40 ml disposable cell culture and antibody production chamber (the 'production module') and a 550 ml medium reservoir (the 'supply module'). The two modules are separated from each other by a dialysis membrane allowing passage of low molecular mass nutrients and metabolites. The monoclonal antibodies are produced and enriched in the production module. The outer part of this module is made from a thin gas-permeable silicone rubber membrane allowing exchange of gases (oxygen and carbon dioxide). To start the culture, the cells are injected into the production module through ports in the silicone rubber which are equipped with Luer Lock connectors. Samples can be removed in the same way. For culturing, the minifermenter is rolled on a roller apparatus in a carbon dioxide-supplied incubator. Depending on the individual properties of the hybridoma cells cultured, cell densities of more than 10 x 10(6) (in some cases up to 35 x 10(6)) cells per ml and monoclonal antibody concentrations of several mg per ml can be obtained in the new minifermenter. On average, 61 mg (range: 9-159 mg) could be produced within 1-4 weeks. In terms of their properties the monoclonal antibodies produced in the new modular minifermenter were indistinguishable from antibodies prepared from ascitic fluid or from the supernatant of conventional stationary culture. The culture method is a useful alternative to the in vivo production method in mice. In addition, it represents a completely new, inexpensive and easy to handle general solution to the problem of culturing cells in high density and obtaining cellular products in high concentrations.

Antibodies, Monoclonal↗