Genomic structure of an economically important cyanobacterium, Arthrospira (Spirulina) platensis NIES-39

A filamentous non-N₂-fixing cyanobacterium, Arthrospira (Spirulina) platensis, is an important organism for industrial applications and as a food supply. Almost the complete genome of A. platensis NIES-39 was determined in this study. The genome structure of A. platensis is estimated to be a single, circular chromosome of 6.8 Mb, based on optical mapping. Annotation of this 6.7 Mb sequence yielded 6630 protein-coding genes as well as two sets of rRNA genes and 40 tRNA genes. Of the protein-coding genes, 78% are similar to those of other organisms; the remaining 22% are currently unknown. A total 612 kb of the genome comprise group II introns, insertion sequences and some repetitive elements. Group I introns are located in a protein-coding region. Abundant restriction-modification systems were determined. Unique features in the gene composition were noted, particularly in a large number of genes for adenylate cyclase and haemolysin-like Ca²⁺-binding proteins and in chemotaxis proteins. Filament-specific genes were highlighted by comparative genomic analysis.

Assessment of vascular supply of hypervascular extra-axial brain tumors with 3T MR regional perfusion imaging

BACKGROUND AND PURPOSE

The vascular supply of extra-axial brain tumors provided by the external carotid artery has not been studied with RPI. The purpose of this work was to determine whether RPI assessment is feasible and provides information on the vascular supply of hypervascular extra-axial brain tumors.

MATERIALS AND METHODS

Conventional ASL and RPI studies were performed at 3T in 8 consecutive patients with meningioma. On the basis of MRA results, we performed RPI by placing a selective labeling slab over the external carotid artery. Five patients underwent DSA before surgery. Two neuroradiologists independently evaluated the overall image quality, the degree of tumor perfusion, and the extent of the tumor vascular territory on conventional ASL and RPI.

RESULTS

In overall quality of conventional ASL and RPI, no images interfered with interpretation. In comparisons of the vascular tumor territory identified by the conventional ASL and RPI techniques, the territories coincided in 3 cases, were partially different in 4, and completely different in 1. The interobserver agreement was very good (kappa = 0.82). In 5 patients who underwent DSA, the 4 patients in whom the dominant supply was the external carotid artery were scored as coincided or partially different. The 1 patient in whom the vascular supply was from the internal carotid artery was scored as completely different.

CONCLUSIONS

RPI with selective labeling of the external carotid artery is feasible and may provide information about the vascular supply of hypervascular extra-axial brain tumors.

Evaluation of dural arteriovenous fistulas with 4D contrast-enhanced MR angiography at 3T

BACKGROUND AND PURPOSE

Four-dimensional contrast-enhanced MR angiography (4D-CE-MRA) at 3T may replace digital subtraction angiography (DSA) for certain diagnostic purposes in patients with intracranial dural arteriovenous fistula (DAVF). The aim of this study was to test the hypothesis that 4D-CE-MRA at 3T enables the same characterization of intracranial DAVFs as DSA.

MATERIALS AND METHODS

The study population consisted of 18 consecutive patients with intracranial DAVFs (11 women, 7 men; age range, 35-82 years; mean age, 64.8 years). They underwent 4D-CE-MRA at 3T and DSA. The 4D-CE-MRA series combined randomly segmented central k-space ordering, keyhole imaging, sensitivity encoding, and half-Fourier imaging. We obtained 30 dynamic scans every 1.9 seconds with a spatial resolution of 1 x 1 x 1.5 mm. Two independent readers reviewed the 4D-CE-MRA images for main arterial feeders, fistula site, and venous drainage. Interobserver and intermodality agreement was assessed by kappa statistics.

RESULTS

At DSA, 8 fistulas were located at the transverse sigmoid sinus; 8, at the cavernous sinus; and 2, at the sinus adjacent to the foramen magnum. Interobserver agreement was fair for the main arterial feeders (kappa = 0.59), excellent for the fistula site (kappa = 0.91), and good for venous drainage (kappa = 0.86). Intermodality agreement was moderate for the main arterial feeders (kappa = 0.68) and excellent for the fistula site (kappa = 1.0) and venous drainage (kappa = 1.0).

CONCLUSIONS

The agreement between 4D-CE-MRA and DSA findings was good to excellent with respect to the fistula site and venous drainage.

Type-B monogalactosyldiacylglycerol synthases are involved in phosphate starvation-induced lipid remodeling, and are crucial for low-phosphate adaptation

Mono- and digalactosyldiacylglycerol (MGDG and DGDG, respectively) constitute the bulk of membrane lipids in plant chloroplasts. Mutant analyses in Arabidopsis have shown that these galactolipids are essential for chloroplast biogenesis and photoautotrophic growth. Moreover, these non-phosphorous lipids are proposed to participate in low-phosphate (Pi) adaptations. Under Pi-limited conditions, a drastic accumulation of DGDG occurs concomitantly with a large reduction in membrane phospholipids, suggesting that plants substitute DGDG for phospholipids during Pi starvation. Previously, we reported that among the three MGDG synthase genes (MGD1, MGD2 and MGD3), the type-B MGD2 and MGD3 are upregulated in parallel with DGDG synthase genes during Pi starvation. Here, we describe the identification and characterization of T-DNA insertional mutants of Arabidopsis type-B MGD genes. Under Pi-starved conditions, the mgd3-1 mutant showed a drastic reduction in DGDG accumulation, particularly in the root, indicating that MGD3 is the main isoform responsible for DGDG biosynthesis in Pi-starved roots. Moreover, in the roots of mgd2 mgd3 plants, Pi stress-induced accumulation of DGDG was almost fully abolished, showing that type-B MGD enzymes are essential for membrane lipid remodeling in Pi-starved roots. Reductions in fresh weight, root growth and photosynthetic performance were also observed in these mutants under Pi-starved conditions. These results demonstrate that Pi stress-induced membrane lipid remodeling is important in plant growth during Pi starvation. The widespread distribution of type-B MGD genes in land plants suggests that membrane lipid remodeling mediated by type-B MGD enzymes is a potent adaptation to Pi deficiency for land plants.

Prognostic value of perfusion MR imaging of high-grade astrocytomas: long-term follow-up study

BACKGROUND AND PURPOSE

Although the prognostic value of perfusion MR imaging in various gliomas has been investigated, that in high-grade astrocytomas alone has not been fully evaluated. The purpose of this study was to evaluate retrospectively whether the tumor maximum relative cerebral blood volume (rCBV) on pretreatment perfusion MR imaging is of prognostic value in patients with high-grade astrocytoma.

MATERIALS AND METHODS

Between January 1999 and December 2002, 49 patients (30 men, 19 women; age range, 23-76 years) with supratentorial high-grade astrocytoma underwent MR imaging before the inception of treatment. The patient age, sex, symptom duration, neurologic function, mental status, Karnofsky Performance Scale, extent of surgery, histopathologic diagnosis, tumor component enhancement, and maximum rCBV were assessed to identify factors affecting survival. Kaplan-Meier survival curves, the logrank test, and the multivariate Cox proportional hazards model were used to evaluate prognostic factors.

RESULTS

The maximum rCBV was significantly higher in the 31 patients with glioblastoma multiforme than in the 18 with anaplastic astrocytoma (P < .03). The 2-year overall survival rate was 67% for 27 patients with a low (< or =2.3) and 9% for 22 patients with a high (>2.3) maximum rCBV value (P < .001). Independent important prognostic factors were the histologic diagnosis (hazard ratio = 9.707; 95% confidence interval (CI), 3.163-29.788), maximum rCBV (4.739; 95% CI, 1.950-11.518), extent of surgery (2.692; 95% CI, 1.196-6.061), and sex (2.632; 95% CI, 1.153-6.010).

CONCLUSION

The maximum rCBV at pretreatment perfusion MR imaging is a useful clinical prognostic biomarker for survival in patients with high-grade astrocytoma.

Optimal contrast medium injection protocols for the depiction of the Adamkiewicz artery using 64-detector CT angiography

AIM

To determine the optimal contrast medium injection protocol for demonstrating the Adamkiewicz artery (AKA) using 64-detector CT angiography (CTA).

MATERIALS AND METHODS

CTA was performed using 64-detector CT. The study population consisted of 80 patients (mean age 67.2 years) with aortoiliac diseases. In the first 60 patients 540 mg I/kg body weight was administered over 25s. The patients were randomly assigned to three protocols with imaging started at 15 (protocol A-1), 18 (A-2), or 21s (A-3) after triggering (threshold 150 HU). The other 20 received 720 mg I/kg body weight with an imaging delay of 18s (protocol B). Two radiologists evaluated the presence of the AKA and measured the attenuation of the aorta and AKA.

RESULTS

Aortic enhancement was 360.4, 348, 279.3, and 372 HU for protocols A-1, A-2, A-3, and B, respectively. There was no significant difference between the A-1 and A-2 protocols (Tukey-Kramer test, p=0.73); however, aortic enhancement was significantly lower in A-3 than A-1 and A-2 (p<0.01). There was no significant difference between A-2 and B (p=0.40). AKA attenuation was 69.3, 91.9, 94.6, and 105.4 HU for protocols A-1, A-2, A-3, and B, respectively. There was no significant difference between the A-2 and A-3 protocols (p=0.91); however, AKA attenuation was significantly lower with A-1 than A-2 or A-3 (p=0.01). AKA attenuation was significantly lower with A-2 than B (p=0.03) and there was a significant difference between A-2 (50%) and B (95%) in the depiction of the hairpin configuration of the AKA (p=0.02).

CONCLUSION

For the demonstration of the AKA at CTA, the optimal protocol used an imaging delay of 18s after triggering and an iodine dose of 720 mg I/kg body weight.

Differentiation between paraclinoid and cavernous sinus aneurysms with contrast-enhanced 3D constructive interference in steady- state MR imaging

BACKGROUND AND PURPOSE

Differentiation between paraclinoid and cavernous sinus aneurysms of the internal carotid artery (ICA) is critical when considering treatment options. The purpose of this study was to determine whether contrast-enhanced (CE) 3D constructive interference in steady state (CISS) MR imaging is useful to differentiate between paraclinoid and cavernous sinus aneurysms.

MATERIALS AND METHODS

This study included 11 aneurysms in 10 consecutive female patients, ranging from 52 to 66 years of age. All aneurysms were adjacent to the anterior clinoid process. After conventional and CE 3D-CISS imaging on a 1.5T MR imaging unit, all patients underwent surgery, and the relationship between the aneurysms and the dura was confirmed. Two neuroradiologists evaluated the location of the aneurysms on CE 3D-CISS images and classified them as intradural, partially intradural, and extradural aneurysms. Operative findings were used as a reference standard. To understand the imaging characteristics, we assessed the boundary and signal intensity of the cavernous sinus, CSF, and carotid artery on the side contralateral to the lesion.

RESULTS

Operative findings disclosed that 5 aneurysms were intradural and 6 were extradural. All except 2 were accurately assessed with CE 3D-CISS imaging. One intradural aneurysm adjacent to a large cavernous aneurysm and 1 cavernous giant aneurysm were assessed as partially intradural. On CE 3D-CISS images, the boundary between the CSF, cavernous sinus, and carotid artery was identified by high signal-intensity contrast in all cases.

CONCLUSION

CE 3D-CISS MR imaging is useful for the differentiation between paraclinoid and cavernous sinus aneurysms.

Digalactosyldiacylglycerol is required for better photosynthetic growth of Synechocystis sp. PCC6803 under phosphate limitation

Digalactosyldiacylglycerol (DGDG) is a typical membrane lipid of oxygenic photosynthetic organisms. Although DGDG synthase genes have been isolated from plants, no homologous gene has been annotated in the genomes of cyanobacteria and the unicellular red alga Cyanidioschyzon merolae. Here we used a comparative genomics approach and identified a non-plant-type DGDG synthase gene (designated dgdA) in Synechocystis sp. PCC6803. The enzyme produced DGDG in Escherichia coli when co-expressed with a cucumber monogalactosyldiacylglycerol synthase. A DeltadgdA knock-out mutant showed no obvious phenotype other than loss of DGDG when grown in a BG11 medium, indicating that DGDG is dispensable under optimal conditions. However, the mutant showed reduced growth under phosphate-limited conditions, suggesting that DGDG may be required under phosphate-limited conditions, such as those in natural niches of cyanobacteria.

Identification of the glycosyl transferase required for synthesis of the principal glycolipid characteristic of heterocysts of Anabaena sp. strain PCC 7120

Nitrogenase is oxygen-labile. Cyanobacterial heterocysts can fix N(2) in an oxic milieu because their interior is micro-oxic, for which the glycolipid layer of the heterocyst envelope is required. ORF all5341 of the Anabaena sp. genome predicts a glycosyl transferase. An insertional mutant of all5341 synthesized only a nonglycosylated form of heterocyst envelope glycolipid, and lacked a glycolipid layer. All5341 appears to be the transferase required to glycosylate the glycolipid aglycone.

Lipid trafficking between the endoplasmic reticulum and the chloroplast

The photosynthetic (thylakoid) membrane of plants is one of the most extensive biological cell membrane systems found in Nature. It harbours the photosynthetic apparatus, which is essential to life on Earth as carbon dioxide is fixed and atmospheric oxygen released by photosynthesis. Lipid biosynthetic enzymes of different subcellular compartments participate in the biogenesis of the thylakoid membrane system. This process requires the extensive exchange of lipid precursors between the chloroplast and the ER (endoplasmic reticulum). The underlying lipid trafficking phenomena are not yet understood at the mechanistic level, but genetic mutants of the model plant Arabidopsis thaliana with disruptions in lipid trafficking between the ER and the chloroplast have recently become available. Their study has led to the identification of components of the lipid transfer machinery at the inner chloroplast envelope.

Comparative genomic analysis revealed a gene for monoglucosyldiacylglycerol synthase, an enzyme for photosynthetic membrane lipid synthesis in cyanobacteria

Cyanobacteria have a thylakoid lipid composition very similar to that of plant chloroplasts, yet cyanobacteria are proposed to synthesize monogalactosyldiacylglycerol (MGDG), a major membrane polar lipid in photosynthetic membranes, by a different pathway. In addition, plant MGDG synthase has been cloned, but no ortholog has been reported in cyanobacterial genomes. We report here identification of the gene for monoglucosyldiacylglycerol (MGlcDG) synthase, which catalyzes the first step of galactolipid synthesis in cyanobacteria. Using comparative genomic analysis, candidates for the gene were selected based on the criteria that the enzyme activity is conserved between two species of cyanobacteria (unicellular [Synechocystis sp. PCC 6803] and filamentous [Anabaena sp. PCC 7120]), and we assumed three characteristics of the enzyme; namely, it harbors a glycosyltransferase motif, falls into a category of genes with unknown function, and shares significant similarity in amino acid sequence between these two cyanobacteria. By a motif search of all genes of Synechocystis, BLAST searches, and similarity searches between these two cyanobacteria, we identified four candidates for the enzyme that have all the characteristics we predicted. When expressed in Escherichia coli, one of the Synechocystis candidate proteins showed MGlcDG synthase activity in a UDP-glucose-dependent manner. The ortholog in Anabaena also showed the same activity. The enzyme was predicted to require a divalent cation for its activity, and this was confirmed by biochemical analysis. The MGlcDG synthase and the plant MGDG synthase shared low similarity, supporting the presumption that cyanobacteria and plants utilize different pathways to synthesize MGDG.

Non-vesicular and vesicular lipid trafficking involving plastids

In plants, newly synthesized fatty acids are either directly incorporated into glycerolipids in the plastid or exported and assembled into lipids at the endoplasmic reticulum (ER). ER-derived glycerolipids serve as building blocks for extraplastidic membranes. Alternatively, they can return to the plastid where their diacylglycerol backbone is incorporated into the glycerolipids of the photosynthetic membranes, the thylakoids. Thylakoid lipids are assembled at the plastid envelope membranes and are transferred to the thylakoids. Under phosphate-limited growth conditions, galactolipids are exported from the outer plastid envelope membranes to extraplastidic membranes. Proteins, such as TRIGALACTOSYLDIACYLGLYCEROL1 (TGD1) or VESICLE-INDUCING PROTEIN IN PLASTIDS1 (VIPP1), which are involved in different aspects of plastid lipid trafficking phenomena have recently been identified and mechanistic models that are based on the analysis of these components have begun to emerge.

Mutation of the TGD1 chloroplast envelope protein affects phosphatidate metabolism in Arabidopsis

Phosphatidate (PA) is a central metabolite of lipid metabolism and a signaling molecule in many eukaryotes, including plants. Mutations in a permease-like protein, TRIGALACTOSYLDIACYLGLYCEROL1 (TGD1), in Arabidopsis thaliana caused the accumulation of triacylglycerols, oligogalactolipids, and PA. Chloroplast lipids were altered in their fatty acid composition consistent with an impairment of lipid trafficking from the endoplasmic reticulum (ER) to the chloroplast and a disruption of thylakoid lipid biosynthesis from ER-derived precursors. The process mediated by TGD1 appears to be essential as mutation of the protein caused a high incidence of embryo abortion. Isolated tgd1 mutant chloroplasts showed a decreased ability to incorporate PA into galactolipids. The TGD1 protein was localized to the inner chloroplast envelope and appears to be a component of a lipid transporter. As even partial disruption of TGD1 function has drastic consequences on central lipid metabolism, the tgd1 mutant provides a tool to explore regulatory mechanisms governing lipid homeostasis and lipid trafficking in plants.

A novel phosphatidylcholine-hydrolyzing phospholipase C induced by phosphate starvation in Arabidopsis

During phosphate starvation, it is known that phospholipids are degraded, and conversely, a nonphosphorus galactolipid digalactosyldiacylglycerol accumulates in the root plasma membrane of plants. We report a novel phospholipase C that hydrolyzes phosphatidylcholine and is greatly induced in response to phosphate deprivation in Arabidopsis. Since phosphatidylcholine-hydrolyzing activity by phospholipase C was highly up-regulated in phosphate-deprived plants, gene expression of some phospholipase C was expected to be induced during phosphate starvation. Based on amino acid sequence similarity to a bacterial phosphatidylcholine-hydrolyzing phospholipase C, six putative phospholipase Cs were identified in the Arabidopsis genome, one of which, NPC4, showed significant transcriptional activation upon phosphate limitation. Molecular cloning and functional expression of NPC4 confirmed that the NPC4 gene encoded a functional phosphatidylcholine-hydrolyzing phospholipase C that did not require Ca(2+) for its activity. Subcellular localization analysis showed that NPC4 protein was highly enriched in the plasma membrane. Analyses of transferred DNA-tagged npc4 mutants revealed that disruption of NPC4 severely reduces the phosphatidylcholine-hydrolyzing phospholipase C activity in response to phosphate starvation. These results suggest that NPC4 plays an important role in the supply of both inorganic phosphate and diacylglycerol from membrane-localized phospholipids that would be used for phosphate supplementation and the replacement of polar lipids in the root plasma membrane during phosphate deprivation.

Arabidopsis type B monogalactosyldiacylglycerol synthase genes are expressed during pollen tube growth and induced by phosphate starvation

The galactolipids monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) constitute the major glycolipids of the thylakoid membranes in chloroplasts. In Arabidopsis, the formation of MGDG is catalyzed by a family of three MGDG synthases, which are encoded by two types of genes, namely type A (atMGD1) and type B (atMGD2 and atMGD3). Although the roles of the type A enzyme have been intensively investigated in several plants, little is known about the contribution of type B enzymes to MGDG synthesis in planta. From our previous analyses, unique expression profiles of the three MGDG synthase genes were revealed in various organs and developmental stages. To characterize the expression profiles in more detail, we performed histochemical analysis of these genes using beta-glucuronidase (GUS) assays in Arabidopsis. The expression of atMGD1::GUS was detected highly in all green tissues, whereas the expression of atMGD2::GUS and atMGD3::GUS was observed only in restricted parts, such as leaf tips. In addition, intense staining was detected in pollen grains of all transformants. We also detected GUS activity in the pollen tubes of atMGD2::GUS and atMGD3::GUS transformants grown in wild-type stigmas but not in atMGD1::GUS, suggesting that type B MGDG synthases may have roles during pollen germination and pollen tube growth. GUS analysis also revealed that expression of atMGD2 and atMGD3, but not atMGD1, are strongly induced during phosphate starvation, particularly in roots. Because only DGDG accumulates in roots during phosphate deprivation, type B MGDG synthases may be acting primarily to supply MGDG as a precursor for DGDG synthesis.

Digalactosyldiacylglycerol is a major glycolipid in floral organs of Petunia hybrida

In higher plants, glycolipids such as monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) are major components of chloroplast membranes in leaves. A recent study identified an isoform of MGDG synthase that is expressed specifically in floral organs, suggesting a novel function for glycolipids in flowers. To elucidate the localization and developmental changes of glycolipids and their biosynthetic activities in flowers, we carried out a series of analytical studies with Petunia hybrida. The results showed that the biosynthetic activities of galactolipid synthesis, particularly for DGDG, increased during flower development. Among the floral organs, the pistil had the highest galactolipid synthetic activity. Its specific activity for incorporation of UDP-galactose to yield galactolipids was estimated to be more than twice that of leaves, which are the major site of galactolipid synthesis in plant tissues. Analysis of lipid contents of pistils revealed that they contained higher amounts of galactolipids than other floral organs. Moreover, DGDG was more abundant than MGDG in both pistils and petals. These results show that DGDG is a major glycolipid in floral organs and that DGDG biosynthetic activity is highly upregulated in the pistils and petals of Petunia flowers.

Light and cytokinin play a co-operative role in MGDG synthesis in greening cucumber cotyledons

The current research investigated the regulation of monogalactosyldiacylglycerol (MGDG) biosynthesis, catalyzed by MGDG synthase (MGD) (UDP-galactose:1,2-diacylglycerol 3-beta-D-galactosyltransferase; EC 2.4.1.46), during chloroplast development in cucumbers (Cucumis sativus L. cv. Aonagajibai). In etiolated seedlings, white light induced a transient increase in MGD mRNA, followed by a subsequent increase in enzyme activity. MGDG, digalactosyldiacylglycerol (DGDG), and linolenic acid (18 : 3) of both MGDG and DGDG accumulated in a light-dependent manner. Early light-dependent induction of MGD protein was also identified in isolated chloroplasts. When cotyledons were detached from seedlings, these light-induced changes diminished. However, when a synthetic cytokinin, benzyladenine, was added to the detached cotyledons, a transient increase in MGD mRNA and a linear increase in the enzyme activity were induced even in the dark. Galactolipids subsequently accumulated to some extent and 18 : 3 content also increased. MGDG fully accumulated in detached cotyledons with co-treatment of light and a cytokinin. Red light (>600 nm) and far-red light (>700 nm) both induced an increase in MGD mRNA and enzyme activity but far-red light did not induce an accumulation of MGDG. These results suggest that (1). galactolipid biosynthesis is regulated by the cooperation of light and a cytokinin; (2). the accumulation of MGDG requires cytokinin in addition to light; (3). a red light (600-700 nm) dependent factor is necessary for the maximal galactolipid accumulation in addition to increase in MGD transcript and activity.

[Development of computerized method for automated classification of the body parts in digital radiographs]

PURPOSE

In picture archiving and communication systems (PACS), the information on the body parts included in radiographs is often not or incorrectly recorded in an image header. In order to apply the computer-aided diagnosis (CAD) system in the PACS environment, the body parts in radiographs need to be recognized correctly by computer. The purpose of this study is to develop a computerized method for correctly classifying the body parts in digital radiographs based on a template matching technique.

METHODS/MATERIALS

The image database used in this study was 1032 digital radiographs (14 x 17 inches) obtained with a computed radiography, and included 505 chest of postetroanterior view, 39 chest of lateral view, 241 abdomen, 108 pelvis, 10 upper limbs, 125 lower limbs, and 4 thoracic spine. In this method, test images were classified into four body parts, i.e., (1) chest, (2) abdomen, (3) pelvis, and (4) upper/lower limbs and thoracic spine. This computerized method was tested with 852 images, since 180 images were employed for creation of 98 templates, which represented the average radiographs for various body parts. Our approach was to examine the similarity of a given test image with templates by use of the cross-correlation values as the similarity measures. The body part of the test image was identified as the body part in the template yielding the maximum correlation value. Our method consisted of the following five steps. First, test images were classified into one of three groups; i.e. 1) chest and abdomen, 2) pelvis, and 3) upper/lower limbs and thoracic spine by using the templates obtained from images with the average size and position. Second, the remaining uncertain images were classified by using additional templates in various directions. Third, the chest and abdomen group was separated into two subgroups; i.e.chest and abdomen. Fourth, in order to classify some uncertain images, templates were shifted horizontally and vertically. Fifth, outer pixels of templates were eliminated to avoid the misclassification due to x-ray collimation.

RESULTS

Our preliminary results indicated that the body parts for 850 cases (99.8%) were correctly classified with our method.

CONCLUSIONS

This method would be useful for automated identification of the body parts in radiographs when various CAD systems would be implemented in the PACS environment.

Identification of two differentially regulated isoforms of protochlorophyllide oxidoreductase (POR) from tobacco revealed a wide variety of light- and development-dependent regulations of POR gene expression among angiosperms

NADPH-protochlorophyllide oxidoreductase (POR) catalyzes the light-dependent reduction of protochlorophyllide a in the chlorophyll biosynthetic pathway. Here, we identified two distinct POR cDNAs from tobacco. Both POR isoforms are encoded by a respective single copy gene in tobacco genome. The overall deduced amino acid sequences of two tobacco cDNAs, designated here POR1 and POR2, displayed significant identities ( approximately 75%), but showed different patterns of light and developmental regulation. In contrast to the previously isolated POR isoforms of Arabidopsis thaliana and barley, the expression of both tobacco POR isoforms were not negatively regulated by light and persisted in matured green tissues. Furthermore, the expression of both genes appeared to be regulated by a diurnal regulation. These results show a wide variety of light- and development-dependent regulations of POR gene expression among angiosperms. Furthermore, phylogenetic analysis including tobacco revealed that POR gene family is differentially represented by angiosperms, most of which is probably caused by independent gene duplication in individual plant. Present results imply a modification of the previous concept that chlorophyll biosynthesis and chloroplast differentiation in angiosperms are ubiquitously controlled by unique functions of two POR isoforms.

Selenium-based digital radiography versus high-resolution storage phosphor radiography in the detection of solitary pulmonary nodules without calcification: receiver operating characteristic curve analysis

OBJECTIVE

The purpose of this study was to compare selenium-based digital radiography with high-resolution storage phosphor radiography for the detection of solitary pulmonary nodules without calcification.

MATERIALS AND METHODS

One hundred twenty-four patients underwent selenium-based digital radiography, high-resolution storage phosphor radiography, and chest CT for evaluation of pulmonary nodules. Thirty-one patients with pulmonary nodules smaller than 3 cm in diameter and 40 patients with normal lungs were selected for receiver operating characteristic curve analysis. Five board-certified radiologists who were unaware of the CT results independently reviewed each of the hard copies of selenium-based digital radiography and storage phosphor radiography, identified pulmonary nodules, and graded their confidence for the presence of each nodule. For each radiologist, we calculated the areas under the receiver operating characteristic curve (AUC) for selenium-based digital radiography and storage phosphor radiography.

RESULTS

The average performance of selenium-based digital radiography (AUC = 0.72) was higher than that of high-resolution storage phosphor radiography (AUC = 0.64), which is statistically significant (p <0.05).

CONCLUSION

Our results indicate that selenium-based digital radiography is superior to high-resolution storage phosphor radiography for detecting solitary pulmonary nodules without calcification.

Two types of MGDG synthase genes, found widely in both 16:3 and 18:3 plants, differentially mediate galactolipid syntheses in photosynthetic and nonphotosynthetic tissues in Arabidopsis thaliana

In Arabidopsis, monogalactosyldiacylglycerol (MGDG) is synthesized by a multigenic family of MGDG synthases consisting of two types of enzymes differing in their N-terminal portion: type A (atMGD1) and type B (atMGD2 and atMGD3). The present paper compares type B isoforms with the enzymes of type A that are known to sit in the inner membrane of plastid envelope. The occurrence of types A and B in 16:3 and 18:3 plants shows that both types are not specialized isoforms for the prokaryotic and eukaryotic glycerolipid biosynthetic pathways. Type A atMGD1 gene is abundantly expressed in green tissues and along plant development and encodes the most active enzyme. Its mature polypeptide is immunodetected in the envelope of chloroplasts from Arabidopsis leaves after cleavage of its transit peptide. atMGD1 is therefore likely devoted to the massive production of MGDG required to expand the inner envelope membrane and build up the thylakoids network. Transient expression of green fluorescent protein fusions in Arabidopsis leaves and in vitro import experiments show that type B precursors are targeted to plastids, owing to a different mechanism. Noncanonical addressing peptides, whose processing could not be assessed, are involved in the targeting of type B precursors, possibly to the outer envelope membrane where they might contribute to membrane expansion. Expression of type B enzymes was higher in nongreen tissues, i.e., in inflorescence (atMGD2) and roots (atMGD3), where they conceivably influence the eukaryotic structure prominence in MGDG. In addition, their expression of type B enzymes is enhanced under phosphate deprivation.