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PubMed1997

ERPs to encoding and recognition in two different inter-item association tasks.

EVENT-RELATED potentials were obtained during study and recognition of word pairs in an incidental learning paradigm. Word pairs were studied either by performing a semantic judgment separately for each word (non-associative encoding) or by creating a semantic association between the two words (associative encoding). Only word pairs encoded associatively elicited a reliable dm-effect with a right frontal maximum. Recognition of previously studied word pairs revealed two topographically and temporally distinct old/new effects: an earlier parietal effect which was only reliable for associatively encoded items and a right frontal effect which was of equal magnitude for word pairs from both encoding tasks. The findings suggest that ERP effects of distinct memory processes are differentially influenced by the encoding instructions.

Adult↗
PubMed2001

Differential activation in parahippocampal and prefrontal cortex during word and face encoding tasks.

Episodic encoding is the first step in the formation of a memory trace. The relation between type of stimulus material and regional brain activation is not fully understood. We measured brain activation using fMRI in 12 healthy subjects during two experiments, word and face encoding. A widespread network of common activations in both tasks was present in the bilateral frontal (BA44/45), occipital (BA17/18/19) and fusiform gyri (BA37) as well as the right hippocampal formation (BA30). A region-of-interest-analysis for the hippocampal formation and dorsolateral prefrontal cortex (DLPFC) was performed additionally. During face encoding the right dorsal and during word encoding the bilateral ventral hippocampal region was activated. In the prefrontal cortex a lateralization to the left side was present only for word encoding. During encoding, activation in the inferior frontal and hippocampal cortex is modulated by the type of stimulus material.

Adult↗
PubMed1996

The presence of two S-layer-protein-encoding genes is conserved among species related to Lactobacillus acidophilus.

Previously we have shown that the type strain of Lactobacillus acidophilus possesses two S-protein-encoding genes, one of which is silent, on a chromosomal segment of 6 kb. The S-protein-encoding gene in the expression site can be exchanged for the silent S-protein-encoding gene by inversion of this slp segment. In this study the presence of S-protein and corresponding S-protein-encoding genes of strains belonging to species that are closely related to L. acidophilus was determined. All strains investigated were identified by numerical comparison of highly standardized one-dimensional SDS-PAGE whole-cellular-protein patterns. Western blot and Southern blot methods were used to identify the presence of, and homology between, S-proteins and S-protein-encoding genes. From these analyses we conclude that strains of L. acidophilus, L. crispatus, L. amylovorus and L. gallinarum possess an S-layer and contain two slp genes. Strains of L. helveticus possess an S-layer but have only one intact slp gene. Strains of L. gasseri, L. johnsonii and L. delbrueckii subsp. bulgaricus have neither an S-layer nor S-protein-encoding genes hybridizing with probes derived from the L. acidophilus slpA or slpB region. The presence of a highly conserved 5' region in the slp genes of strains of L. acidophilus, L. crispatus, L. amylovorus and L. gallinarum suggests that S-layer variation is a common feature for strains of these species.

Bacterial Proteins↗
PubMed1999

Isolation of the gene encoding an immunodominant membrane protein of the apple proliferation phytoplasma, and expression and characterization of the gene product.

An immunodominant membrane protein (IMP) of the apple proliferation (AP) phytoplasma was detected in preparations from AP-diseased periwinkle plants using monoclonal and polyclonal antibodies to the AP agent. Following isolation from Western blots and partial sequencing, degenerate oligonucleotides derived from the IMP sequence were used as probes to identify a DNA fragment containing the ORF encoding the IMP. Complete sequencing and subsequent analysis of the cloned DNA fragment revealed the presence of two ORFs, predicted to encode proteins with molecular masses of 25 kDa (P-318A) and 19 kDa (P-318B). Whilst database searches failed to assign a possible function to P-318A, analysis of P-318B predicted an amphiphilic membrane protein with a positively charged N-terminal portion, followed by a hydrophobic segment forming an alpha-helix, and a hydrophilic C-terminal part located outside of the cell. The amphiphilic nature of P-318B was confirmed by its solubility in Triton X-114. The gene encoding P-318B was expressed in Escherichia coli and the resulting protein was used to immunize rabbits. The antiserum obtained reacted specifically with P-318B. The same protein was also detected by an antiserum raised against antigen preparations from AP-diseased plants. The P-318B antiserum did not react with antigen preparations from plants infected with the closely related pear decline phytoplasma. However, in Southern hybridization studies, the gene encoding the IMP hybridized to genomic fragments of the pear decline and European stone fruit yellows phytoplasmas. It also showed significant sequence similarity to a gene encoding an antigenic membrane protein of the sweet potato witches' broom phytoplasma, but not to a gene encoding a major immunogenic membrane protein of an aster yellows group phytoplasma. Since it appears that most phytoplasmas possess a major immunogenic membrane protein which may have a function in pathogenesis, this work may be a basis for further studies on fundamental aspects of host-pathogen interactions. It also describes a new approach to obtain suitable immunogens to produce specific antibodies for detection and characterization of the non-culturable phytoplasmas.

Amino Acid Sequence↗
PubMed2003

Analysis of mRNA with microsomal fractionation using a SAGE-based DNA microarray system facilitates identification of the genes encoding secretory proteins.

In the regulation of host defense responses such as inflammation and immunity, the secretory proteins, including membrane proteins, play central roles. Although many secretory proteins have been identified by using methods such as differential display, random screening, or the signal sequence trap method, each method suffers from poor reproducibility, low sensitivity, or time-consuming or laborious work. Therefore, the strategy for facilitating the selection of the genes encoding the secretory proteins is desired. In this paper, we describe a system for isolating the genes encoding secretory proteins by analyzing mRNAs with microsomal fractionation on serial analysis of gene expression (SAGE)-based DNA microarray system. This system succeeded in discriminating the genes encoding secretory proteins from ones encoding nonsecretory proteins with 80% accuracy. We applied this system to human T lymphocytes. As a result, we were able to identify the genes that are not only encoding secretory proteins but also expressing selectively in a specific subset of T lymphocytes. The SAGE-based DNA microarray system is a promising system to identify the genes encoding specific secretory proteins.

Amino Acid Sequence↗
PubMedDate not supplied

Disconnection analysis of CA3 and DG in mediating encoding but not retrieval in a spatial maze learning task.

The dentate gyrus (DG) subregion of the hippocampus has been shown to be involved in encoding but not retrieval in a spatial maze task (modified Hebb-Williams maze). The first experiment in this study examined whether a lesion to the CA3 would contribute to a similar encoding deficit. A DG group was included in order to replicate previous results. Relative to controls, animals receiving CA3 lesions were impaired in encoding, not retrieval, on the modified Hebb-Williams maze--similar to a group that received DG lesions. This suggests the possibility that CA3 and DG are working together to mediate encoding processes. The second experiment in this study was designed to test the interaction between CA3 and DG using a disconnection paradigm. Animals with contralateral lesions (CA3 lesioned in one hemisphere, DG lesioned in the other hemisphere) showed a significant disruption effect on encoding, but not retrieval, when compared with animals with ipsilateral lesions (CA3 and DG lesioned in the same hemisphere, leaving the other hemisphere intact). This suggests an interaction between CA3 and DG in supporting encoding but not retrieval processes in a spatial maze learning task.

Animals↗
PubMed2002

The bifunctional LKR/SDH locus of plants also encodes a highly active monofunctional lysine-ketoglutarate reductase using a polyadenylation signal located within an intron.

Both plants and animals catabolize lysine (Lys) via two consecutive enzymes, Lys-ketoglutarate reductase (LKR) and saccharopine dehydrogenase (SDH), which are linked on a single polypeptide encoded by a single LKR/SDH gene. We have previously shown that the Arabidopsis LKR/SDH gene also encodes a monofunctional SDH that is transcribed from an internal promoter. In the present report, we have identified two cDNAs derived from cotton (Gossypium hirsutum) boll abscission zone that encode a novel enzymatic form of Lys catabolism, i.e. a catabolic monofunctional LKR. The monofunctional LKR mRNA is also encoded by the LKR/SDH gene, using two weak polyadenylation sites located within an intron. In situ mRNA hybridization and quantitative reverse transcriptase-polymerase chain reaction analyses also suggest that the cotton monofunctional LKR is relatively abundantly expressed in parenchyma cells of the abscission zone. DNA sequence analysis of the LKR/SDH genes of Arabidopsis, maize (Zea mays), and tomato (Lycopersicon esculentum) suggests that these genes can also encode a monofunctional LKR mRNA by a similar mechanism. To test whether the LKR/SDH and monofunctional LKR enzymes possess different biochemical properties, we used recombinant Arabidopsis LKR/SDH and monofunctional LKR enzymes expressed in yeast (Saccharomyces cerevisiae) cells. The K(m) of the monofunctional LKR to Lys was nearly 10-fold lower than its counterpart that is linked to SDH. Taken together, our results suggest that the LKR/SDH locus of plants is a super-composite locus that can encode three related but distinct enzymes of Lys catabolism. These three enzymes apparently operate in concert to finely regulate Lys catabolism during plant development.

Arabidopsis↗
PubMed2002

Characterization of the genes encoding the cytosolic and plastidial forms of ADP-glucose pyrophosphorylase in wheat endosperm.

In most species, the synthesis of ADP-glucose (Glc) by the enzyme ADP-Glc pyrophosphorylase (AGPase) occurs entirely within the plastids in all tissues so far examined. However, in the endosperm of many, if not all grasses, a second form of AGPase synthesizes ADP-Glc outside the plastid, presumably in the cytosol. In this paper, we show that in the endosperm of wheat (Triticum aestivum), the cytosolic form accounts for most of the AGPase activity. Using a combination of molecular and biochemical approaches to identify the cytosolic and plastidial protein components of wheat endosperm AGPase we show that the large and small subunits of the cytosolic enzyme are encoded by genes previously thought to encode plastidial subunits, and that a gene, Ta.AGP.S.1, which encodes the small subunit of the cytosolic form of AGPase, also gives rise to a second transcript by the use of an alternate first exon. This second transcript encodes an AGPase small subunit with a transit peptide. However, we could not find a plastidial small subunit protein corresponding to this transcript. The protein sequence of the purified plastidial small subunit does not match precisely to that encoded by Ta.AGP.S.1 or to the predicted sequences of any other known gene from wheat or barley (Hordeum vulgare). Instead, the protein sequence is most similar to those of the plastidial small subunits from chickpea (Cicer arietinum) and maize (Zea mays) and rice (Oryza sativa) seeds. These data suggest that the gene encoding the major plastidial small subunit of AGPase in wheat endosperm has yet to be identified.

Amino Acid Sequence↗
PubMed2000

anthocyanin1 of petunia encodes a basic helix-loop-helix protein that directly activates transcription of structural anthocyanin genes.

The petunia loci anthocyanin1 (an1), an2, an4, and an11 are required for the transcription of anthocyanin biosynthetic genes in floral organs. The an2 and an11 loci were recently cloned and shown to encode a MYB-domain transcriptional activator and a cytosolic WD40 protein, respectively. Here, we report the isolation of an1 by transposon tagging. an1 encodes a new member of the basic helix-loop-helix family of transcription factors that is functionally and evolutionarily distinct from JAF13, the apparent petunia ortholog of maize RED1 and snapdragon DELILA. We provide genetic evidence that the transcription factors encoded by an1, an2, and an4 operate in an unexpectedly complex regulatory hierarchy. In leaves, ectopic expression of AN2 induces an1 expression, whereas in anthers, an1 expression depends on an4, encoding (or controlling) a MYB protein that is paralogous to AN2. Experiments with transgenic plants expressing a post-translationally controlled AN1-GLUCOCORTICOID RECEPTOR fusion protein indicated that independent of protein synthesis, AN1 directly activates the expression of the dfrA gene encoding the enzyme dihydroflavonol 4-reductase and of Pmyb27 encoding a MYB-domain protein of unknown function.

Amino Acid Sequence↗
PubMed2006

Evolving compact and interpretable Takagi-Sugeno fuzzy models with a new encoding scheme.

Developing Takagi-Sugeno fuzzy models by evolutionary algorithms mainly requires three factors: an encoding scheme, an evaluation method, and appropriate evolutionary operations. At the same time, these three factors should be designed so that they can consider three important aspects of fuzzy modeling: modeling accuracy, compactness, and interpretability. This paper proposes a new evolutionary algorithm that fulfills such requirements and solves fuzzy modeling problems. Two major ideas proposed in this paper lie in a new encoding scheme and a new fitness function, respectively. The proposed encoding scheme consists of three chromosomes, one of which uses unique chained possibilistic representation of rule structure. The proposed encoding scheme can achieve simultaneous optimization of parameters of antecedent membership functions and rule structures with the new fitness function developed in this paper. The proposed fitness function consists of five functions that consider three evaluation criteria in fuzzy modeling problems. The proposed fitness function guides evolutionary search direction so that the proposed algorithm can find more accurate compact fuzzy models with interpretable antecedent membership functions. Several evolutionary operators that are appropriate for the proposed encoding scheme are carefully designed. Simulation results on three modeling problems show that the proposed encoding scheme and the proposed fitness functions are effective in finding accurate, compact, and interpretable Takagi-Sugeno fuzzy models. From the simulation results, it is shown that the proposed algorithm can successfully find fuzzy models that approximate the given unknown function accurately with a compact number of fuzzy rules and membership functions. At the same time, the fuzzy models use interpretable antecedent membership functions, which are helpful in understanding the underlying behavior of the obtained fuzzy models.

Algorithms↗
PubMed2004

IP-10-encoding plasmid DNA therapy exhibits anti-tumor and anti-metastatic efficiency.

We report here that the interferon-induced protein of 10 kDa (IP-10 or CXCL10) elicits strong anti-tumor and anti-metastatic responses in mice when administered by plasmid DNA. Intratumoral but not intramuscular IP-10 DNA inoculation resulted in reduced tumor formation of malignant melanoma (B16F10) and Lewis lung carcinoma (LL/2) in C57BL/6 mice. In addition, plasmid DNA-encoding IP-10 substantially reduced the establishment of metastases when injected systemically by the intramuscular route. In contrast to the primary tumor model, the anti-metastatic effect of DNA-encoding IP-10 was primarily mediated by NK cells. Compared to DNA-encoding interleukin-12 (IL-12), therapy with DNA-encoding IP-10 exhibits lower efficacy against primary melanoma tumors but equivalent efficacy against primary Lewis lung tumors and against B16F10 lung metastasis formation. Co-administration of DNA-encoding IP-10 and IL-12 enhanced the anti-tumor activity of IL-12 in the lung metastasis model but had little effect in the local treatment of established subcutaneous tumors. Interestingly, treatment of nude mice lacking T lymphocytes with DNA-encoding IP-10 or IL-12 still resulted in a pronounced reduction of tumor growth or metastasis formation.

Animals↗
PubMed1996

Identification and characterization of a mobilizing plasmid, pND300, in Lactococcus lactis M189 and its encoded nisin resistance determinant.

A 60 kb conjugative plasmid, pND300, which encodes nisin resistance, was identified in Lactococcus lactis ssp. lactis (L. lactis) M189. pND300 was found to mobilize the transfer of some other plasmids as indicated by the mobilization of plasmids encoding lactose utilization. The nisin resistance determinant from pND300 was initially subcloned on a 12 kb DNA fragment and subsequently reduced to 10.4 kb. Restriction analysis, PCR, Southern hybridization and sequencing illustrated that the nisin resistance of pND300 is very similar to that encoded by the transposon involved in nisin production. pND300 encodes nisR as well as nisK and the recently reported nisF, nisE and nisG, but does not encode nisI. The DNA fragment encoding the nis genes is flanked by IS946 with a copy at each end in reverse orientation. The expression of these nis genes is probably controlled by a putative promoter upstream of nisR, which is composed of the TTGCAA hexanucleotide on the insertion sequence IS946 and the TATAAT sequence 21 bp downstream.

Base Sequence↗
PubMed2004

Deletion of the genes encoding the MtrA-MtrB two-component system of Corynebacterium glutamicum has a strong influence on cell morphology, antibiotics susceptibility and expression of genes involved in osmoprotection.

The MtrAB two-component signal transduction system is highly conserved in sequence and genomic organization in Mycobacterium and Corynebacterium species, but its function is completely unknown. Here, the role of MtrAB was studied with C. glutamicum as model organism. In contrast to M. tuberculosis, it was possible to delete the mtrAB genes in C. glutamicum. The mutant cells showed a radically different cell morphology and were more sensitive to penicillin, vancomycin and lysozyme but more resistant to ethambutol. In order to identify the molecular basis for this pleiotropic phenotype, the mRNA profiles of mutant and wild type were compared with DNA microarrays. Three genes showed a more than threefold increased RNA level in the mutant, i.e. mepA (NCgl2411) encoding a putative secreted metalloprotease, ppmA (NCgl2737 ) encoding a putative membrane-bound protease modulator, and lpqB encoding a putative lipoprotein of unknown function. Expression of plasmid-encoded mepA in Escherichia coli led to elongated cells that were hypersensitive to an osmotic downshift, supporting the idea that peptidoglycan is the target of MepA. The mRNA level of two genes was more than fivefold decreased in the mutant, i.e. betP and proP which encode transporters for the uptake of betaine and proline respectively. The microarray results were confirmed by primer extension and RNA dot blot experiments. In the latter, the transcript level of genes involved in osmoprotection was tested before and after an osmotic upshift. The mRNA level of betP, proP and lcoP was strongly reduced or undetectable in the mutant, whereas that of mscL (mechanosensitive channel) was increased. The changes in cell morphology, antibiotics susceptibility and the mRNA levels of betP, proP, lcoP, mscL and mepA could be reversed by expression of plasmid-encoded copies of mtrAB in the DeltamtrAB mutant, confirming that these changes occurred as a consequence of the mtrAB deletion.

ATP-Binding Cassette Transporters↗
PubMed1994

The cross-reactive idiotopes recognized by the monoclonal antibodies 9G4 and LC1 are located in framework region 1 of two non-overlapping subsets of human VH4 family encoded antibodies.

The monoclonal anti-idiotopic antibodies LC1 and 9G4 bind two non-overlapping sets of VH4 encoded antibodies. 9G4 exclusively binds VH4-21 encoded antibodies, while LC1 binds antibodies derived from VH4 family gene segments V71-2, V71-4, VH4-18, VH72-1 and V2-1. The VH4-21 gene segment is utilized by most cold agglutinin (CA) antibodies with I/i specificity, while antibodies encoded by other VH4 gene segments are associated not with CA disease, but primarily with rheumatoid-factor (RF) activity. We previously determined that the idiotope to which 9G4 binds in VH4-21-derived antibodies is located in framework region 1 (FR1). In the present study, by using mutational analysis involving individual framework- and complementarity-determining region exchanges between VH4-21- and V71-2-encoded antibodies, we have found that the idiotope to which LC1 binds in V71-2-derived antibodies also maps to FR1. The LC1 idiotope is heavy (H)-chain associated, but requires pairing with a light (L) chain for LC1 binding. Recombinant antibodies composed of a variety of kappa (kappa) and lambda (lambda) L chains paired with either a V71-2 or VH4-21 chain were produced in the baculovirus expression system. LC1 bound all of the kappa-containing antibodies but did not bind the V71-2-encoded H chain alone nor to the two lambda-containing antibodies. This experiment demonstrates that not all light chains exert equivalent influence on the conformation of the H-chain idiotope. These results indicate that the FR1 of VH4-encoded antibodies is immunogenic and suggest a physiological role of FR1 during an immune response.

Amino Acid Sequence↗
PubMed1990

The 2-oxoglutarate dehydrogenase complex from Azotobacter vinelandii. 2. Molecular cloning and sequence analysis of the gene encoding the succinyltransferase component.

The nucleotide sequence encoding the succinyltransferase component (E2o) of the 2-oxoglutarate dehydrogenase complex from Azotobacter vinelandii has been determined. Previously the cloning in Escherichia coli of the gene encoding lipoamide dehydrogenase from A. vinelandii was reported [Westphal, A.H. & de Kok, A. (1988) Eur. J. Biochem. 172, 299-305]. The 3.2-kb fragment used for the sequence determination contained the main part of the gene encoding succinyltransferase. The complete E2o gene, as well as the gene encoding the 2-oxoglutarate dehydrogenase component, resided on a 14.7-kb fragment from which the 3.2-kb fragment was subcloned. The protein-coding sequence of the gene consists of 1200 bp (400 codons, including the AUG start codon and the UGA stop codon). It is separated from the gene encoding the 2-oxoglutarate dehydrogenase component by 42 bp. No E. coli-like promoter sequence was found. A putative ribosome-binding site is located 9-15 bp upstream from the start codon. No terminator sequences were found downstream of the stop codon. This makes it likely that the three genes of the oxoglutarate dehydrogenase complex are transcribed as a single mRNA transcript analogous to the pyruvate dehydrogenase complex in E. coli. The intact gene was subcloned from the 14.7-kb fragment and brought to high expression under the influence of the vector-encoded lacZ promoter. The similarity with the E. coli enzyme is high with 63% identity. Like the enzyme from E. coli, it consists of a single lipoyl-binding domain, a putative E1- and E3-binding domain and a catalytic domain. The main difference is found in a 31-residue sequence rich in alanine and proline located between the lipoyl domain and the putative E1- and E3-binding domain. This sequence, usually found in acetyltransferases and there identified as a highly mobile region by 1H-NMR, is replaced by a more polar, charged region in the E. coli enzyme.

Acyltransferases↗
PubMed1996

Mutational analysis of the nor gene cluster which encodes nitric-oxide reductase from Paracoccus denitrificans.

The genes that encode the hc-type nitric-oxide reductase from Paracoccus denitrificans have been identified. They are part of a cluster of six genes (norCBQDEF) and are found near the gene cluster that encodes the cd1-type nitrite reductase, which was identified earlier [de Boer, A. P. N., Reijnders, W. N. M., Kuenen, J. G., Stouthamer, A. H. & van Spanning, R. J. M. (1994) Isolation, sequencing and mutational analysis of a gene cluster involved in nitrite reduction in Paracoccus denitrificans, Antonie Leeu wenhoek 66, 111-127]. norC and norB encode the cytochrome-c-containing subunit II and cytochrome b-containing subunit I of nitric-oxide reductase (NO reductase), respectively. norQ encodes a protein with an ATP-binding motif and has high similarity to NirQ from Pseudomonas stutzeri and Pseudomonas aeruginosa and CbbQ from Pseudomonas hydrogenothermophila. norE encodes a protein with five putative transmembrane alpha-helices and has similarity to CoxIII, the third subunit of the aa3-type cytochrome-c oxidases. norF encodes a small protein with two putative transmembrane alpha-helices. Mutagenesis of norC, norB, norQ and norD resulted in cells unable to grow anaerobically. Nitrite reductase and NO reductase (with succinate or ascorbate as substrates) and nitrous oxide reductase (with succinate as substrate) activities were not detected in these mutant strains. Nitrite extrusion was detected in the medium, indicating that nitrate reductase was active. The norQ and norD mutant strains retained about 16% and 23% of the wild-type level of NorC, respectively. The norE and norF mutant strains had specific growth rates and NorC contents similar to those of the wild-type strain, but had reduced NOR and NIR activities, indicating that their gene products are involved in regulation of enzyme activity. Mutant strains containing the norCBQDEF region on the broad-host-range vector pEG400 were able to grow anaerobically, although at a lower specific growth rate and with lower NOR activity compared with the wild-type strain.

Amino Acid Sequence↗
PubMed2006

An asymmetry between memory encoding and retrieval. Revelation, generation, and transfer-appropriate processing.

Transfer-appropriate-processing accounts of memory emphasize the similarity of encoding and retrieval processes, and imply that experimental manipulations should have similar effects on encoding and retrieval. Exceptions to this expectation are thus of great interest, but extant exceptions (produced by studies using divided attention, alcohol, and benzodiazepines) are debatable, single dissociations between encoding and retrieval. The present experiments demonstrate a reversed dissociation, in which the same variable produced opposite effects when implemented at encoding and retrieval. At encoding, participants either solved anagrams of study words or read intact study words. At retrieval, participants likewise solved anagrams or read intact words prior to making recognition memory judgments. Compared with reading intact words, solving anagrams at encoding enhanced later recognition accuracy, whereas solving anagrams at test impaired accuracy. These results were obtained with old/new decisions (Experiment 1) and with confidence ratings (Experiment 2).

Adult↗
PubMedDate not supplied

Phase-encode order and its effect on contrast and artifact in single-shot RARE sequences.

Substantial manipulation of tissue contrast can be achieved by varying the order in which phase-encode values are applied to individual echoes within a 128-echo single-shot rapid acquisition relaxation enhanced (RARE) sequence. Appropriate ordering can then permit imaging of short T2 species like muscle and white matter with single-shot RARE. For sequential phase encoding with an arbitrary initial phase-encode value, the timing of the zero phase (ZP) encoded echo is found to be analogous to the echo time (TE) of standard spin-echo sequences. This is demonstrated qualitatively with human brain images and is verified quantitatively with NiCl2 phantoms by correlating the time constant for signal decay with ZP echo time, with transverse relaxation times T2, as obtained with a 128-echo Carr-Purcell-Meiboom-Gill (CPMG) imaging sequence. Banding artifacts accompanying the discontinuous traverse through K space are experimentally demonstrated in a rectangular phantom and expressions are developed for determining the dependence of this artifact on the phase-encode gradient increments and durations, the ZP echo number, echo spacing, and T2. Simulations based on the expressions are shown to be useful for characterizing the observed "banding" artifacts perpendicular to the phase-encode direction and for predicting the extent of tissue-tissue overlap to be expected with the use of this ultrafast rf echo planar imaging method.

Brain↗