[The DICOM-CD-Project of the German Radiology Association--an overview of the content and results of a pilot study in 2006]. / Das DICOM-CD-Projekt der Deutschen Röntgengesellschaft--eine Ubersicht über die Inhalte und Ergebnisse des Pilottests 2006.

DICOM-CDs are frequently used for medical image data transfer. Many different potential advantages are known, such as improved image quality, handling simplification, and cost optimization. However, there are numerous restrictions in the daily routine. While testing DICOM-CDs at the 2006 German Radiology Congress, we found that more than 70 % of CDs have discrepancies with respect to data structure or content. The German Radiological Association and OFFIS started an initiative to improve the quality of DICOM-CDs. There are three main objectives: To provide requirements for vendors of CD-writing systems, to establish user guidelines for the handling of DICOM-CDs, and to develop a test procedure for DICOM-CDs. Radiologists using such systems should be aware of these developments and use them for RFP's.

[Standards for safe data exchange in teleradiology exemplified by image and report distribution]. / Standards für den sicheren Datenaustausch in der Teleradiologie am Beispiel der Bild- und Befundverteilung.

The use of telemedicine is becoming indispensable for a continuous and economical delivery of a high quality of care. However, data protection requirements have to be considered. For the selection of solutions, vendor-independent components based on standards are a prerequisite for a seamless integration into the existing, often heterogeneous, IT infrastructure. The "Internet protocol" TCP/IP and the DICOM standard with it's new security extensions form the basis for an internationally standardized and accepted procedure for a secure interchange of radiological images beyond platform boundaries.

Cardiac digital image loops and multimedia reports over the internet using DICOM.

The authors define an open, scaleable telemedicine architecture to reduce the time of reports delivery and consultation; increasing their simplicity via introducing common image presentation, storage and telecommunication formats and methods for telecardiology. They've developed a software application to implement it introducing the most appropriate digital imaging methods and formats using the latest available technology.

DICOM extensions for narrow-band networks.

DICOM is today's de-facto standard for exchanging medical images. Since new image acquisition devices produce more and more image and non-image data, image compression has become an important part of the standard. However, the compression of non-pixel data also stored in DICOM data sets has been disregarded up to now. In the scope of an EU research project we have examined a large amount of real-world DICOM images to test whether or not there is a potential for compressing the non-pixel attributes. Especially for use with narrow-band networks extensions as proposed in this paper could be a solution to save valuable bandwidth.

New DICOM extensions for softcopy and hardcopy display consistency.

The DICOM standard defines in detail how medical images can be communicated. However, the rules on how to interpret the parameters contained in a DICOM image which deal with the image presentation were either lacking or not well defined. As a result, the same image frequently looks different when displayed on different workstations or printed on a film from various printers. Three new DICOM extensions attempt to close this gap by defining a comprehensive model for the display of images on softcopy and hardcopy devices: Grayscale Standard Display Function, Grayscale Softcopy Presentation State and Presentation Look Up Table.

Tuber-specific expression of a yeast invertase and a bacterial glucokinase in potato leads to an activation of sucrose phosphate synthase and the creation of a sucrose futile cycle.

Fluxes were investigated in growing tubers from wild-type potato (Solanum tuberosum L. cv.Desiree) and from transformants expressing a yeast invertase in the cytosol under the control of the tuber-specific patatin promoter either alone (EC 3.2.1.26;U-IN2-30) or in combination with a Zymomonas mobilis glucokinase (EC 2.7.1.2; GK3-38) by supplying radiolabelled [14C]sucrose, [14C]glucose or [14C]fructose to tuber discs for a 90-min pulse and subsequent chase incubations of 4 and 12 h, and by supplying [14C]fructose for 2 h and 4 h to intact tubers attached to the mother plant. Contrary to the expectation that this novel route for sucrose degradation would promote starch synthesis,the starch content decreased in the transgenic lines.Labelling kinetics did not reveal whether this was due to changes in the fluxes into or out of starch. However,they demonstrated that glycolysis is enhanced in the transgenic lines in comparison to the wild type. There was also a significant stimulation of sucrose synthesis,leading to a rapid cycle of sucrose degradation and resynthesis. The labelling pattern indicated that sucrose phosphate synthase (SPS; EC 2.4.1.14) was responsible for the enhanced recycling of label into sucrose. In agreement, there was a 4-fold and 6-fold increase in the activation status of SPS in U-IN2-30 and GK3-38,respectively, and experiments with protein phosphatase inhibitors indicated that this activation involves enhanced dephosphorylation of SPS. It is proposed that this activation of SPS is promoted by the elevated glucose 6-phosphate levels in the transgenic tubers.These results indicate the pitfalls of metabolic engineering without a full appreciation of the metabolic system and regulatory circuits present in the tissue under investigation.

Combined expression of glucokinase and invertase in potato tubers leads to a dramatic reduction in starch accumulation and a stimulation of glycolysis.

The original aim of this work was to increase starch accumulation in potato tubers by enhancing their capacity to metabolise sucrose.We previously reported that specific expression of a yeast invertase in the cytosol of tubers led to a 95% reduction in sucrose content, but that this was accompanied by a larger accumulation of glucose and a reduction in starch. In the present paper we introduced a bacterial glucokinase from Zymomonas mobilis into an invertase-expressing transgenic line, with the intention of bringing the glucose into metabolism. Transgenic lines were obtained with up to threefold more glucokinase activity than in the parent invertase line and which did not accumulate glucose. Unexpectedly, there was a further dramatic reduction in starch content, down to 35% of wild-type levels. Biochemical analysis of growing tuber tissue revealed large increases in the metabolic intermediates of glycolysis, organic acids and amino acids,two- to threefold increases in the maximum catalytic activities of key enzymes in the respiratory pathways, and three- to fivefold increases in carbon dioxide production.These changes occur in the lines expressing invertase,and are accentuated following introduction of the second transgene, glucokinase. We conclude that the expression of invertase in potato tubers leads to an increased flux through the glycolytic pathway at the expense of starch synthesis and that heterologous overexpression of glucokinase enhances this change in partitioning.

Two cDNAs from potato are able to complement a phosphate uptake-deficient yeast mutant: identification of phosphate transporters from higher plants.

Acquisition as well as translocation of phosphate are essential processes for plant growth. In many plants, phosphate uptake by roots and distribution within the plant are presumed to occur via a phosphate/proton cotransport mechanism. Here, we describe the isolation of two cDNAs, StPT1 and StPT2, from potato (Solanum tuberosum) that show homology to the phosphate/proton cotransporter PHO84 from the yeast Saccharomyces cerevisiae. The predicted products of both cDNAs share 35% identity with the PHO84 sequence. The deduced structure of the encoded proteins revealed 12 membrane-spanning domains with a central hydrophilic region. The molecular mass was calculated to be 59 kD for the StPT1 protein and 58 kD for the StPT2 protein. When expressed in a PHO84-deficient yeast strain, MB192, both cDNAs complemented the mutant. Uptake of radioactive orthophosphate by the yeast mutant expressing either StPT1 or StPT2 was dependent on pH and reduced in the presence of uncouplers of oxidative phosphorylation, such as 2,4-dinitrophenol or carbonyl cyanide m-chlorophenylhydrazone. The K(m) for Pi uptake of the StPT1 and StPT2 proteins was determined to be 280 and 130 microM, respectively. StPT1 is expressed in roots, tubers, and source leaves as well as in floral organs. Deprivation of nitrogen, phosphorus, potassium, and sulfur changed spatial expression as well as the expression level of StPT1. StPT2 expression was detected mainly in root organs when plants were deprived of Pi and to a lesser extent under sulfur deprivation conditions. No expression was found under optimized nutrition conditions or when other macronutrients were lacking.

Two genes encoding extension-like proteins are predominantly expressed in tomato root hair cells.

A differential screen of a tomato root hair cDNA library resulted in the cloning of two cDNAs, Dif10 and Dif54, whose corresponding genes are preferentially expressed in root hair cells as determined by analysis of mRNA levels in various tomato organs. Transcript levels showed no increase in leaves subjected to hormonal and environmental stress treatments. Sequence analysis of the cDNAs revealed high similarity to members of the extension family. Extensions are hydroxyproline-rich glycoproteins (HRGPs) located in the cell wall. In order to study the functional significance of HRGPs in root hairs, tomato seedling roots were treated with micromolar concentrations of 3,4-dehydro-L-proline (Dhp), a selective inhibitor of prolyl hydroxylase. Dhp treatment resulted in changes in root growth and the development of root hairs with reduced hair length, suggesting an important role of HRGPs in hair morphogenesis.

Cutting, ageing and expression of plant membrane transporters.

The activity and the expression of sucrose, hexose and amino acid transporters were studied with fresh, cut or aged tissues and plasma membrane vesicles (PMV) of mature sugar beet (Beta vulgaris L.) leaves. Cutting and ageing both induced an increase of the transcripts coding for sucrose transporters and hexose transporters. No significant effect could be detected on the amino acid transporter transcripts with the probe used (aap1). A polyclonal serum directed against the Arabidopsis thaliana sucrose transporter (AtSUC1) reacted with a 42 kDa band of the sugar beet PMV, confirming previous biochemical identification of this band as a sucrose transporter. ELISA assays run with microsomal fractions and PMV using the AtSUC1 sucrose transporter probe indicated that ageing, and to a lesser extent cutting, increased the amount of sucrose transporter present in the plasma membrane. However, while cutting strongly stimulated proton-motive force driven uptake of sucrose in PMV, ageing only resulted in a slight stimulation. These data give evidence for transcriptional, post-transcriptional and post-translational controls of the activity of the sucrose transporter by mechanical treatments. Proton-motive force driven uptake of 3-O-methylglucose and valine in PMV was strongly stimulated in PMV from aged tissues, although previous data had shown that cutting did not affect theses processes. Therefore, the plant cells possess various levels of control mechanisms that allow them to regulate fluxes of the main assimilates across the plasma membrane when their natural environment is directly or indirectly altered.

Preferential expression of an ammonium transporter and of two putative nitrate transporters in root hairs of tomato.

Root hairs as specialized epidermal cells represent part of the outermost interface between a plant and its soil environment. They make up to 70% of the root surface and, therefore, are likely to contribute significantly to nutrient uptake. To study uptake systems for mineral nitrogen, three genes homologous to Arabidopsis nitrate and ammonium transporters (AtNrt1 and AtAmt1) were isolated from a root hair-specific tomato cDNA library. Accumulation of LeNrt1-1, LeNrt1-2, and LeAmt1 transcripts was root-specific, with no detectable transcripts in stems or leaves. Expression was root cell type-specific and regulated by nitrogen availability. LeNrt1-2 mRNA accumulation was restricted to root hairs that had been exposed to nitrate. In contrast, LeNrt1-1 transcripts were detected in root hairs as well as other root tissues under all nitrogen treatments applied. Analogous to LeNrt1-1, the gene LeAmt1 was expressed under all nitrogen conditions tested, and root hair-specific mRNA accumulation was highest following exposure to ammonium. Expression of LeAMT1 in an ammonium uptake-deficient yeast strain restored growth on low ammonium medium, confirming its involvement in ammonium transport. Root hair specificity and characteristics of substrate regulation suggest an important role of the three genes in uptake of mineral nitrogen.

Isolation and characterization of two cDNA clones encoding ATP-sulfurylases from potato by complementation of a yeast mutant.

Sulfur plays an important role in plants, being used for the biosynthesis of amino acids, sulfolipids and secondary metabolites. After uptake sulfate is activated and subsequently reduced to sulfide or serves as donor for sulfurylation reactions. The first step in the activation of sulfate in all cases studied so far is catalyzed by the enzyme ATP-sulfurylase (E.C. 2.7.7.4.) which catalyzes the formation of adenosine-5'-phosphosulfate (APS). Two cDNA clones from potato encoding ATP-sulfurylases were identified following transformation of a Saccharomyces cerevisiae mutant deficient in ATP-sulfurylase activity with a cDNA library from potato source leaf poly(A)+ RNA cloned in a yeast expression vector. Several transformants were able to grow on a medium with sulfate as the only sulfur source, this ability being strictly linked to the presence of two classes of cDNAs. The clones StMet3-1 and StMet3-2 were further analyzed. DNA analysis revealed an open reading frame encoding a protein with a molecular mass of 48 kDa in the case of StMet3-1 and 52 kDa for StMet3-2. The deduced polypeptides are 88% identical at the amino acid level. The clone StMet3-2 has a 48 amino acid N-terminal extension which shows common features of a chloroplast transit peptide. Sequence comparison of the ATP-sulfurylase Met3 from Saccharomyces cerevisiae with the cDNA StMet3-1 (StMet3-2) reveals 31% (30%) identity at the amino acid level. Protein extracts from the yeast mutant transformed with the clone StMet3-1 displayed ATP-sulfurylase activity. RNA blot analysis demonstrated the expression of both genes in potato leaves, root and stem, but not in tubers.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence for an essential role of the sucrose transporter in phloem loading and assimilate partitioning.

Sucrose is the principal transport form of assimilates in most plants. In many species, translocation of assimilates from the mesophyll into the phloem for long distance transport is assumed to be carrier mediated. A putative sucrose proton cotransporter cDNA has been isolated from potato and shown to be expressed mainly in the phloem of mature exporting leaves. To study the in vivo role and function of the protein, potato plants were transformed with an antisense construct of the sucrose transporter cDNA under control of the CaMV 35S promoter. Upon maturation of the leaves, five transformants that expressed reduced levels of sucrose transporter mRNA developed local bleaching and curling of leaves. These leaves contained > 20-fold higher concentrations of soluble carbohydrates and showed a 5-fold increase in starch content as compared with wild type plants, as expected from a block in export. Transgenic plants with a reduced amount of sucrose carrier mRNA show a dramatic reduction in root development and tuber yield. Maximal photosynthetic activity was reduced at least in the strongly affected transformants. The effects observed in the antisense plants strongly support an apoplastic model for phloem loading, in which the sucrose transporter located at the phloem plasma membrane represents the primary route for sugar uptake into the long distance distribution network.

Potato sucrose transporter expression in minor veins indicates a role in phloem loading.

The major transport form of assimilates in most plants is sucrose. Translocation from the mesophyll into the phloem for long-distance transport is assumed to be carrier mediated in many species. A sucrose transporter cDNA was isolated from potato by complementation of a yeast strain that is unable to grow on sucrose because of the absence of an endogenous sucrose uptake system and the lack of a secreted invertase. The deduced amino acid sequence of the potato sucrose transporter gene StSUT1 is highly hydrophobic and is 68% identical to the spinach sucrose transporter SoSUT1 (pS21). In yeast, the sensitivity of sucrose transport to protonophores and to an increase in pH is consistent with an active proton cotransport mechanism. Substrate specificity and inhibition by protein modifiers are similar to results obtained for sucrose transport into protoplasts and plasma membrane vesicles and for the spinach transporter, with the exception of a reduction in maltose affinity. RNA gel blot analysis shows that the StSUT1 gene is highly expressed in mature leaves, whereas stem and sink tissues, such as developing leaves, show only low expression. RNA in situ hybridization studies show that the transporter gene is expressed specifically in the phloem. Both the properties and the expression pattern are consistent with a function of the sucrose transporter protein in phloem loading.

Expression cloning in yeast of a cDNA encoding a broad specificity amino acid permease from Arabidopsis thaliana.

To study amino acid transport in plants at the molecular level, we have isolated an amino acid permease cDNA from Arabidopsis thaliana by complementation of a yeast mutant defective in proline uptake with a cDNA. The predicted polypeptide of 53 kDa is highly hydrophobic with 12 putative membrane-spanning regions and shows no significant homologies to other known transporters. Expression of the cDNA enables the yeast mutant to take up L-[14C]proline. Competition studies argue for a broad but stereospecific substrate recognition by the permease, which resembles neutral or general amino acid transport systems from Chlorella and higher plants. Both pH dependence and inhibition by protonophores are consistent with a proton symport mechanism.

Antisense repression of the chloroplast triose phosphate translocator affects carbon partitioning in transgenic potato plants.

The major chloroplast envelope membrane protein E29 is central for the communication between chloroplasts and cytosol. It has been identified as the triose phosphate translocator (TPT) exporting the primary products of the Calvin cycle (i.e., triose phosphates and 3-phosphoglycerate) out of the chloroplast in a strict counter exchange for Pi. To study the in vivo role of the TPT, transgenic potato plants were constructed that have a reduced expression of the TPT at both the RNA and protein level due to antisense inhibition. Chloroplasts isolated from these plants show a 20-30% reduction with respect to their ability to import Pi. The reduced TPT activity leads to a reduction of maximal photosynthesis by 40-60%, to a change in carbon partitioning into starch at the expense of sucrose and amino acids, and to an increase of the leaf starch content by a factor of approximately 3. At early developmental stages the inhibited plants are retarded in growth compared to the wild type.

Isolation and characterization of a sucrose carrier cDNA from spinach by functional expression in yeast.

Active loading of the phloem with sucrose in leaves is an essential part of the process of supplying non-photosynthetic tissues with carbon and energy. The transport is protein mediated and coupled to proton-symport, but so far no sucrose carrier gene has been identified. Using an engineered Saccharomyces cerevisiae strain, a cDNA from spinach encoding a sucrose carrier was identified by functional expression. Yeast strains that allow the phenotypic recognition of a sucrose carrier activity were constructed by expressing a cytoplasmic invertase from yeast, or the potato sucrose synthase gene, in a strain unable to transport or grow on sucrose due to a deletion in the SUC2 gene. A spinach cDNA expression library established from the poly(A)+ RNA from source leaves of spinach and cloned in a yeast expression vector yielded transformed yeast clones which were able to grow on media containing sucrose as the sole carbon source. This ability was strictly linked to the presence of the spinach cDNA clone pS21. Analysis of the sucrose uptake process in yeast strains transformed with this plasmid show a pH-dependent uptake of sucrose with a Km of 1.5 mM, which can be inhibited by maltose, alpha-phenylglucoside, carbonyl cyanide m-chlorophenylhydrazone and p-chloromercuribenzenesulfonic acid. These data are in accordance with measurements using both leaf discs and plasma membrane vesicles from leaves of higher plants. DNA sequence analysis of the pS21 clone reveals the presence of an open reading frame encoding a protein with a molecular mass of 55 kDa. The predicted protein contains several hydrophobic regions which could be assigned to 12 membrane-spanning regions.(ABSTRACT TRUNCATED AT 250 WORDS)