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At least 1,297 records · Page 72Linked to original sources
PubMed2002

Hepatic malignant tumour versus cavernous haemangioma: differentiation on multiple breath-hold turbo spin-echo MRI sequences with different T2-weighting and T2-relaxation time measurements on a single slice multi-echo sequence.

AIM: We evaluated the signal intensity change on breath-hold turbo spin-echo (TSE) T2-weighted sequences using different echo times (TE) and T2-relaxation time measurements on a single slice eight-echo sequence in the differentiation of hepatic malignancy from cavernous haemangioma. MATERIALS AND METHODS: Breath-hold TSE T2-weighted axial images of the liver were performed at TEs of 80, 120 and 160 ms in 34 patients with focal liver lesions (13 with cavernous haemangiomas, 14 with hepatocellular carcinomas and seven with metastases). The lesion percentage signal intensity change on the lower TE image to the higher TE image was calculated. T2-relaxation time was measured on a single slice eight-echo sequence. RESULTS: The TE pair 80/160 ms on breath-hold TSE T2-weighted sequences gave a performance (100% sensitivity, 92% specificity, 95% positive predictive value and 100% negative predictive value) better than other TE pairs in differentiating haemangioma from malignancy. Addition of fat-suppression compromised the diagnostic performance for all TE-pairs. The use of T2 relaxation time threshold of < 112 ms as indicative of malignant lesion achieved a 100% sensitivity, 77% specificity, 88% positive predictive value and 100% negative predictive value. CONCLUSION: Percentage signal intensity change on breath-hold TSE T2-weighted sequences at TE 80/160 ms appears to be a quick and potentially useful means of differentiating hepatic malignancy from haemangioma.

Adult↗
PubMed1992

[MR tomography in testicular processes. The significance of Gd-DTPA enhanced sequences in comparison with plain T2-weighted sequences].

The value of T1-weighted sequences after intravenous administration of Gd-DTPA and of T2-weighted sequences was compared in 43 patients suspected of having scrotal abnormalities. T2-weighted sequences gave better demonstration of the tunica albuginea and better contrast between tumor and parenchyma. The two techniques were equally sensitive for demonstrating testicular tumors but orchitis was better demonstrated on the contrast enhanced sequences. Motion artifacts were less marked in the T1-weighted sequences with contrast enhancement. In selected cases, contrast enhancement may be a valuable addition to native protocols. Our experience has indicated that MRI provides specific findings in cases of orchitis which are clinically atypical; this facilitates the decision to conservative treatment and prevents unnecessary exploration of the testes.

Adolescent↗
PubMed1988

[Spin-echo sequences and rapid image sequences in a comparison of spinal diseases].

Rapid image sequences of the spine were compared with proton and T2-weighted spin-echo sequences in 30 patients concerning their diagnostic value and image contrast. The rapid series was carried out with an angle of rotation of 30%, TR of 21 and TE of 12 msec., the spin-echo sequences with a TR/TE of 2,000/20/80 msec. The quality and contrast of the rapid series was markedly inferior to the spin-echo sequences; this was particularly marked for demonstrating disc and bone degeneration. At present, the routine use of rapid sequences cannot be recommended as a substitute for spine-echo examinations.

Humans↗
PubMed1988

[Parameter-weighted MR images and their optimization: theory and example of images for the flash sequence compared to the spin-echo sequence].

In this paper the signal intensity and parameter-weighting zones of spin echo and gradient echo sequences (FLASH) have been analysed. Using information available in the literature, with additional analytical and numerical techniques, it is possible to determine parameters which maximise tissue contrast for T1, T2 and proton-weighted images. The technique is equally applicable to spin echo and FLASH sequences. The advantages of optimised gradient echo sequences compared with spin echo sequences with respect to its signal to noise ratio for short repetition times are analysed quantitatively. T2-weighted images can be generated as rapid as T1-weighted images, using the FLASH sequences when using a small angle of spin and relatively long echo. Illustrations are shown to demonstrate the numerical results (field strength 1.5 tesla). This is followed by a discussion of possible opposing effects.

Humans↗
PubMed1983

Avian carcinoma virus MH2 contains a transformation-specific sequence, mht, and shares the myc sequence with MC29, CMII, and OK10 viruses.

Avian carcinoma virus MH2 has been grouped together with MC29, CMII, and OK10, because all of these viruses share a transformation-specific sequence termed myc. A 5.2-kilobase (kb) DNA provirus of MH2 has been molecularly cloned. The complete genetic structure of MH2 is 5'-delta gag(1.9-kb)-mht(1.2-kb)-myc(1.3-kb)-delta env(?) and noncoding c-region (0.2-kb)-3'. delta gag, delta env, and c are genetic elements shared with nondefective retroviruses, whereas mht is a unique, possibly MH2 transformation-specific, sequence. Hybridizations with normal chicken DNA and cloned chicken c-myc DNA indicate that the mht sequence probably derives from a normal cellular gene that is distinct from the c-myc gene. The genetic structure of MH2 suggests that the delta gag and mht sequences function as a hybrid gene that encodes the p100 putative transforming protein. The myc sequence of MH2 appears to encode a second transforming function. Therefore, it seems that MH2 contains two genes with possible oncogenic function, whereas MC29, CMII, and OK10 each carries a single hybrid delta gag-myc transforming gene. It is remarkable that, despite these fundamental differences in their primary structures and mechanisms of gene expression, MH2 and MC29 have very similar oncogenic properties.

Cell Transformation, Viral↗
PubMedDate not supplied

Comparison of magnetic resonance imaging sequences with computed tomography to detect low-grade subarachnoid hemorrhage: Role of fluid-attenuated inversion recovery sequence.

OBJECTIVES: To compare computed tomography (CT) with magnetic resonance imaging (MRI) for the presumptive diagnosis and localization of acute and subacute low-grade subarachnoid hemorrhage (SAH). METHODS: We consecutively enrolled 45 patients clinically suspected of low-grade SAH, comparing them with a control group. We obtained axial nonenhanced CT scans as well as fluid-attenuated inversion recovery (FLAIR) and T2-weighted gradient echo (T2*) MRI sequences at 1.0 T. Two neuroradiologists scrutinized the presence of blood at 26 different regions in the intracranial subarachnoid space (SAS). RESULTS: Three of 45 patients had normal CT and MRI scans, and SAH was excluded by lumbar puncture. We demonstrated SAH on CT scans in 28 of 42 (66.6%) patients, T2* sequences in 15 of 42 (35.7%) patients, and FLAIR sequences in 42 of 42 (100%) patients. Fluid-attenuated inversion recovery sequences were superior to CT in 16 of the 26 evaluated regions. CONCLUSIONS: The FLAIR sequence was superior for presumptive diagnosis and localization of acute and subacute low-grade SAH, representing a potential tool in this setting.

Adolescent↗
PubMedDate not supplied

Analysis of sequence-dependent interactions between transient calcium and transmitter stimuli in activating adenylyl cyclase in Aplysia: possible contribution to CS--US sequence requirement during conditioning.

An important recent insight in a number of neurobiological systems is that during learning, individual dually regulated proteins with associative properties function as critical sites of stimulus convergence. During conditioning in Aplysia, the Ca2+ /calmodulin-sensitive adenylyl cyclase (AC) in mechanosensory neurons serves as a molecular site of interaction between Ca2+ and serotonin [5-hydroxytryptamine (5-HT)]-two signals that represent the CS and US in these cells. Conditioning requires that the CS and US be paired within a narrow time window and in the appropriate sequence. AC shows an analogous sequence preference: It is more effectively activated when a pulse of Ca2+ precedes a pulse of 5-HT than when the 5-HT precedes Ca2+. One mechanism that contributes to this sequence preference is that Ca2+/calmodulin binding to AC accelerates the rate of AC activation by receptor-Gs. We have identified two additional properties of AC activation that would cause pairing with Ca2+ preceding 5-HT to be more effective than simultaneous pairing or pairing with the reciprocal sequence: (1) Activation of Aplysia AC by a Ca2+ pulse rose with a delay compared with activation by a 5-HT pulse. (2) A late pulse of Ca2+, which arrived after 5-HT, acted, via calmodulin, to accelerate the decay of AC activation by receptor-Gs. Together, these activation properties of AC may contribute to the CS-US sequence requirement of classical conditioning.

Adenylyl Cyclases↗
PubMed1987

Homology of pCS1 Plasmid Sequences with Chromosomal DNA in Clavibacter michiganense subsp. sepedonicum: Evidence for the Presence of a Repeated Sequence and Plasmid Integration.

Restriction fragments of pCS1, a 50.6-kilobase (kb) plasmid present in many strains of Clavibacter michiganense subsp. sepedonicum ("Corynebacterium sepedonicum"), have been cloned in an M13mp11 phage vector. Radiolabeled forms of these cloned fragments have been used as Southern hybridization probes for the presence of plasmid sequences in chromosomal DNA of this organism. These studies have shown that all tested strains lacking the covalently closed circular form of pCS1 contain the plasmid in integrated form. In each case the site of integration exists on a single plasmid restriction fragment with a size of 5.1 kb. Southern hybridizations with these probes have also revealed the existence of a major repeated sequence in C. michiganense subsp. sepedonicum. Hybridizations of chromosomal DNA with deletion subclones of a 2.9-kb plasmid fragment containing the repeated sequence indicate that the size of the repeated sequence is approximately 1.3 kb. One of the copies of the repeated sequence is on the plasmid fragment containing the site of integration.

Journal Article↗
PubMed2004

Multiplex PCR genotyping assay that distinguishes between isolates of Clostridium perfringens type A carrying a chromosomal enterotoxin gene (cpe) locus, a plasmid cpe locus with an IS1470-like sequence, or a plasmid cpe locus with an IS1151 sequence.

Clostridium perfringens type A isolates carrying the enterotoxin (cpe) gene are important causes of both food poisoning and non-food-borne diarrheas in humans. In North America and Europe, food poisoning isolates were previously shown to carry a chromosomal cpe gene, while non-food-borne gastrointestinal (GI) disease isolates from those two geographic locations were found to have a plasmid cpe gene. In this report, we describe the development of an economical multiplex PCR cpe genotyping assay that works with culture lysates to distinguish among type A isolates carrying a chromosomal cpe gene, a plasmid cpe gene with a downstream IS1470-like sequence, or a plasmid cpe gene with a downstream IS1151 sequence. When this multiplex PCR assay was applied in molecular epidemiologic studies, it was found that (i) all 57 examined type A isolates with a plasmid cpe gene have either IS1470-like or IS1151 sequences downstream of the plasmid cpe gene; (ii) an IS1470-like sequence, rather than an IS1151 sequence, is more commonly present downstream of the plasmid cpe gene (particularly in North American non-food-borne human GI disease isolates); and (iii) as previously shown in the United States and Europe, isolates carrying the chromosomal cpe gene also appear to be the major cause of C. perfringens food poisoning in Japan. The superiority of this new multiplex PCR assay over existing cpe genotyping approaches should facilitate further molecular epidemiologic investigations of C. perfringens enterotoxin-associated GI illnesses and their associated cpe-positive type A isolates.

Bacterial Typing Techniques↗
PubMed1998

Antipredictable sequences: harder to predict than random sequences.

For any discrete-state sequence prediction algorithm A, it is always possible, using an algorithm B no more complicated than A, to generate a sequence for which A's prediction is always wrong. For any prediction algorithm A and sequence x, there exists a sequence y no more complicated than x, such that if A performs better than random on x, then it will perform worse than random on y by the same margin. An example of a simple neural network predicting a bit sequence is used to illustrate this very general but not widely recognized phenomenon. This implies that any predictor with good performance must rely on some (usually implicitly) assumed prior distributions of the problem.

Algorithms↗
PubMed2000

Can different levels of S-R practice influence sequence learning? An investigation into the context of a perceptual-motor sequence learning task.

The main aim of the present study was to evaluate on a serial reaction time task the effect of stimulus-response (S-R) practice on sequence learning. The experiment used a pointing task which allowed recording reaction times and movement times. The basic manipulation consisted in varying the amount of S-R practice prior to sequence practice. Two main findings from this study may be highlighted. Firstly, the benefit from extensive S-R practice was mainly observed in the random practice phase. Secondly, S-R learning and sequence learning were reflected by different components of performance. The movement times were selectively sensitive to the acquisition of S-R regularities whereas the reaction times were selectively sensitive to the acquisition of sequence regularities. The implications of these results on the comprehension of the sequence learning mechanism were then discussed.

Adult↗
PubMed1998

Sequencing of PCR amplified HBV DNA pre-c and c regions in the 2.2.15 cells and antiviral action by targeted antisense oligonucleotide directed against sequence.

AIM:To study the specific inhibition of HBV gene expression by liver-targeting antisense oligonucleotide (ASON) directed against pre-c and cregious in a sequence specific manner.METHODS:According to the result of direct sequencing of PCR amplified products, a 16 mer phosphorothioate analogue of the antisense oligonucleotide (PS-ASOn) directed against the HBV U-5-like region was synthesized and then linked with one live-targeting ligand, the galactosylated poly-L-lysine.Their effect on the expression of HBV gene was observed using the 2.2.15 cells.RESULTS:HBV DNA in the 2.2.15 cells was from HBV with surface antigen subtype ayw 1 by sequencing so that antisense oligonucleotides could bind specifically to the target sequence through base piring. Under the same experimental conditions, the inhibitory rates of PS-ASON to HBsAg and HBeAg were 70% and 58% at a concentration of 10&mgr;mol/L, while by ligand-PS-ASON they were 96% and 82%, the amount of HBV DNA in cultured supernatant and cells was reduced significantly. An unrelated sequence oligonucleotide showed no effectiveness. All the oligonucleotides had no cytotoxicity.CONCLUSION:Antisense oligonucleotides complexed by the liver-targeting ligand can be targeted to cells via asialoglycoprotein receptors, resulting in supecific inhibition of HBV gene expression and replication.

Journal Article↗
PubMed2001

Purine-rich exon sequences are not necessarily splicing enhancer sequence in the dystrophin gene.

Purine-rich sequences within exons are proposed to promote proper splicing as splicing enhancers. In order to test this supposition in the dystrophin gene, which is characterized by the large size of its introns, purine-rich sequences from three exons (exons 43, 46 and 53) were examined for their splicing enhancer activity by using a Drosophila doublesex pre-mRNA. The most powerful activating effect on upstream intron splicing was seen with a sequence from exon 43. A sequence from exon 53 showed relatively low activity, whilst that from exon 46 had little effect. To characterize the splicing enhancer sequences in exons 53 and 46 further, entire exons were divided into 30nt fragments that were examined separately for their splicing enhancer activity. In exon 53, two fragments located at the 5' and 3' ends, respectively, had strong splicing enhancer activity, although they were not the most purine-rich regions of the exon. In contrast, all of the fragments derived from exon 46 had little activity. These results suggest that different exons in the dystrophin transcript are subject to different mechanisms of control by the splicing machinery.

Animals↗
PubMed2002

[The true recognizing sequence of the restriction enzyme whose recognizing sequence is nonpalindromic].

The recognizing sequence of restriction enzyme includes palindrome and nonpalindromic, and DNA is double helix complementary strands. So the recognizing sequences of palindrome enzyme in two strands of DNA were identical,and can be considered of one sequence. But for nonpalindromic restriction enzyme,the recognizing sequences of two strands of DNA were not identical. Therefore the true recognizing sequences are not only one. In this experiment,an enzyme cleavage reaction was carried out which confirmed that the true recognizing sites/sequences of nonpalindromic enzyme are two instead of one.

English Abstract↗
PubMed1997

Laser scanning confocal microscopy and factor analysis of biomedical image sequences (FAMIS) to detect and characterise HPV DNA sequences by FISH in HeLa cells.

Visualisation and localisation of specific DNA sequences were performed by fluorescence in situ hybridisation (FISH), confocal laser scanning microscopy (CLSM), and factor analysis of biomedical image sequences (FAMIS). HeLa cells containing 10-50 copies per cell of human papillomavirus (HPV) DNA type 18 integrated in cellular DNA were used as a model. HPV-DNA was identified by DNA probes and DNA-DNA hybrids were revealed by alkaline phosphatase and Fast Red (FR) TR salt/naphtol-MX phosphate. Cell nuclei were counterstained with thiazole orange (TO). FAMIS summarises image sequences into a reduced number of images called factor images and curves called factors. Factor images correspond to spatial distributions of the different factors. Factors estimate different individual physical behaviours in the sequence (extinction velocity, spectral emission, depth emission profiles). We verified that HPV-DNA hybridisation signals are specific to the spectrum of FR, and distinguished between FR and TO. The latter result was found by taking into account differences in their extinction velocities. The focus of CLSM was improved on 3D image sequences, and the location of fluorescent signals inside the preparations was determined. Factor images showed that FR stained targets were located on different focal planes at the periphery of the nuclei.

DNA, Viral↗
PubMed1993

Expressed human immunoglobulin kappa genes and their hypermutation.

The question of which germ-line V kappa genes are expressed was studied by sequencing 70 different cDNA clones from a human spleen library and one clone from a fetal liver library. The sequences were compared to a data base containing all germ-line V kappa gene and pseudogene sequences. In addition, 51 rearranged genomic V kappa genes, 170 cDNA and 74 kappa proteins from the literature were assigned to specific germ-line V kappa genes and included in the comparisons. Not all the known, potentially functional V kappa genes were found to be expressed, while some genes with minor defects are. The total number of expressed genes is smaller than expected: so far 21 germ-line genes and 5 pairs of duplicated identical genes are known to be transcribed. The corresponding numbers for rearranged genomic V kappa genes and kappa proteins are 17 plus 4 and 7 plus 7, respectively. A second aim of the study was to find out whether the expressed repertoire contains derivatives of germ-line V kappa genes still missing in our data base; no evidence for the existence of such genes was found. Several cDNA clones contained additional nucleotides between the V kappa and J kappa gene segments, which may be germ-line derived, inserted by terminal deoxynucleotidyl transferase or introduced by other mechanisms. Somatic gene conversion seems not to play a major role in creating the human kappa gene diversity. Various aspects of the hypermutation of kappa genes are discussed and the formation of block mutations, i.e. the alterations of two or more adjacent nucleotides is stressed as a remarkable feature of the process.

Amino Acid Sequence↗
PubMed2001

The rat interleukin 10 receptor: cloning and sequencing of cDNA coding for the alpha-chain protein sequence, and demonstration by western blotting of expression in the rat brain.

cDNA coding for the alpha chain of the rat interleukin 10 (IL-10) receptor was amplified by polymerase chain reaction (PCR), cloned and sequenced. The nucleic acid coding sequence exhibited 88% and 68% homology with the mouse and human IL-10 receptor sequences, respectively. The translated protein exhibited 83% and 61% homology with the mouse and human IL-10 receptor proteins. Specific antibodies were raised to the extracellular domain of the rat IL-10 receptor expressed as a secreted protein in recombinant Drosophila S2 cells. Western blotting using these antibodies demonstrated the presence of the IL-10 receptor in five major regions of the rat brain (cortex, cerebellum, hippocampus, hypothalamus and pituitary), supporting a role for IL-10 as a central regulator of inflammation.

Amino Acid Sequence↗
PubMed1993

The complete amino acid sequence for brain beta spectrin (beta fodrin): relationship to globin sequences.

The amino acid sequence of mouse brain beta spectrin (beta fodrin), deduced from the nucleotide sequence of complementary DNA clones, reveals that this non-erythroid beta spectrin comprises 2363 residues, with a molecular weight of 274,449 Da. Brain beta spectrin contains three structural domains and we suggest the position of several functional domains including f-actin, synapsin I, ankyrin and spectrin self association sites. Analysis of deduced amino acid sequences indicated striking homology and similar structural characteristics of brain beta spectrin repeats beta 11 and beta 12 to globins. In vitro analysis has demonstrated that heme is capable of specific attachment to brain spectrin, suggesting possible new functions in electron transfer, oxygen binding, nitric oxide binding or heme scavenging.

Actins↗