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At least 1,477 records · Page 82Linked to original sources
PubMed2006

Linear measures of temporal lobe atrophy on brain magnetic resonance imaging (MRI) but not visual rating of white matter changes can help discrimination of mild cognitive impairment (MCI) and Alzheimer's disease (AD).

Clinical discrimination of the early stages of AD and MCI is challenging. MRI indices which are simple enough to be applied by non-radiologists on hard copies would be of practical importance in the discrimination. We studied 45 consecutive patients (17 with MCI, 25 with AD, 3 with normal cognitive findings) with at least one white matter lesion (WML) on axial fluid-attenuated inversion recovery (FLAIR) MRI sequences. WML load was evaluated by Fazekas' scoring system; temporal lobe atrophy by interuncal distance (IUD) measurement. WML pattern had no significant discriminative value of AD and MCI. No significant correlation between periventricular/subcortical WML scores and neuropsychological test results was observed. The mean IUD was significantly smaller in patients with MCI compared to those with AD. The cut-off value of IUD was 28.3 mm with receiver operating curve (ROC) analysis. Area under the curve was 0.925 (95% CI: 0.800-0.983). A significant negative correlation between IUD and the mini mental state examination (MMSE), verbal fluency, clock drawing, and Rey Auditory verbal learning test (AVLT) was noted. The results indicate that measurement of IUD is a clinically useful test in discrimination of AD and MCI patients with WML(s) on brain MRI. However, severity of these lesions is not useful for distinctions.

Aged↗
PubMed2005

T-DNA tagging and characterization of a cryptic root-specific promoter in Arabidopsis.

From a T-DNA tagged Arabidopsis population, a line, M-57 showing GUS (beta-glucuronidase) expression in the vascular regions of young roots was identified. Southern analysis revealed presence of a single T-DNA insert. Using inverse PCR, the plant sequence flanking the T-DNA insertion was cloned. The insertion was identified to be in the intergenic area between loci At4G13940 and At4G13930, coding for SAHH (S-Adenosyl-l-Homocysteine Hydrolase) and SHMT (Serine Hydroxy Methyl Transferase) genes, respectively. A 452-bp fragment immediately upstream of the T-DNA insertion when cloned and mobilized as a GUS fusion was capable of driving a similar root-specific expression of reporter gene in transgenic Arabidopsis plants and their progenies. This cryptic promoter element does not show the presence of any known root-specific promoter element.

Arabidopsis↗
PubMed2005

Synthesis of 2,3:4,6-di-O-isopropylidene-D-allopyranose from D-glucose.

2,3:4,6-Di-O-isopropylidene-d-allopyranose can be conveniently prepared from d-glucose via a synthetic sequence, which includes Mitsunobu inversion at O-3, di-O-isopropylidenation of phenyl-1-thio-d-alloside and anomeric deprotection on treatment with NBS/CaCO3.

Carbohydrate Conformation↗
PubMed1993

MRI diffusion-weighted imaging of the brain: contributions to image contrast from CSF signal reduction, use of a long echo time and diffusion effects.

The contributions of CSF signal reduction, use of a long echo time and diffusion weighting to the appearance of pulsed gradient spin echo (PGSE) images are analysed by reference to T2-weighted spin echo and T2-weighted fluid attenuated inversion recovery (FLAIR) pulse sequences. Both PGSE and T2-weighted FLAIR sequences reduce CSF signal and produce very heavy T2 weighting allowing the specific additional contribution produced by the diffusion weighting of PGSE sequences to be recognized. Considerable advantage accrues from CSF suppression with both PGSE and FLAIR sequences through reduction in partial volume effects and artefacts. The very heavy T2 weighting with both these pulse sequences highlights certain white matter tracts and provides high sensitivity to disease. The additional diffusion weighting with PGSE sequences can enhance or reduce white matter tract signals and may enhance or reduce lesion conspicuity relative to the FLAIR sequences. Many of the benefits attributed to the diffusion-weighted PGSE sequence may result from the reduction of the CSF signal and the heavy T2 weighting of the sequence without a contribution from diffusion effects. However, additional anatomical detail, sensitivity to myelination and increased lesion conspicuity may result from the diffusion weighting.

Brain↗
PubMed1995

Normal variation in the magnetic resonance imaging appearances of the sacroiliac joints: pitfalls in the diagnosis of sacroiliitis.

The purpose of this paper is to define the normal and variable appearances of the sacroiliac joints and adjacent subchondral marrow on unenhanced and enhanced Magnetic Resonance Imaging (MRI). Twenty subjects were imaged with spin-echo T1-weighted (T1), fast spin-echo T2-weighted (T2), T1-weighted with fat suppression (T1FS) and fast short tau inversion recovery (Fast STIR) sequences. Five of these subjects were imaged following intravenous Gd-DTPA administration, and the enhancement factor of the synovial compartment of the sacroiliac joint and subchondral marrow was calculated. The appearance of the cartilage of the synovial compartment on T1 and T2 images is of an intermediate signal bounded by signal void of bone cortex. On T1FS and Fast STIR images the cartilage has an intermediate to high signal. The marrow on T1, T2 and T1FS images has a homogeneous intermediate signal. T1FS images demonstrate the synovial compartment with greater clarity than T1 images. Cortical erosions and subchondral sclerosis were not demonstrated in our subjects, and partial volume artifact between the synovial and ligamentous compartments should not be interpreted as erosions. On Fast STIR images there is normally a region of high signal from the immediate subchondral marrow, which should not be interpreted as early sacroiliitis. Seven subjects demonstrated a patchy distribution of fat within the bone marrow, an appearance which alone does not indicate sacroiliitis. One subject had an accessory articular facet of the sacroiliac joint. The percentage maximal enhancement factor of the synovial compartment of the sacroiliac joint and adjacent subchondral marrow is 52% and 94% on T1FS images respectively. These figures redefine the normal maximal enhancement factors in this region of the body.

Adipose Tissue↗
PubMed1998

Clone-specific high-frequency retrotransposition of a recombinant virus containing a VL30 promoter in SV40-transformed NIH3T3 cells.

A recombinant virus, containing the promoter of a VL30 LTR and tagged with the neomycin gene as a selection and indicator marker, was constructed to investigate transposition events in NIH3T3 cells after SV40 transformation. This retroviral construct was transfected into psi/CRE packaging cells, and pseudovirions were used to infect NIH3T3 cells. Clones resistant to G418 bearing single-copy integrations of the recombinant virus were isolated and transformed by SV40 virus. Transpositions were detected through RFLPs with a neomycin probe and 'retrotransposition' was further confirmed by inverse PCR and DNA sequencing of transposed and parental copies. We found that: (1) retrotransposition of this recombinant virus occurred with a high frequency in a parental clone transformed with SV40 virus suggesting that the frequency of retrotransposition depended on the initial site of provirus integration; (2) the transposition frequency was independent of the transcription level of the recombinant construct; and (3) analysis of transposition-positive transformants showed that the high transposition frequency appeared to be associated with the induction of endogenous reverse transcriptases.

3T3 Cells↗
PubMed2001

Assessment of cerebrovascular reactivity with functional magnetic resonance imaging: comparison of CO(2) and breath holding.

Cerebral blood flow (CBF) and oxygenation changes following both a simple breath holding test (BHT) and a CO(2) challenge can be detected with functional magnetic resonance imaging techniques. The BHT has the advantage of not requiring a source of CO(2) and acetazolamide and therefore it can easily be performed during a routine MR examination. In this study we compared global hemodynamic changes induced by breath holding and CO(2) inhalation with blood oxygenation level dependent (BOLD) and CBF sensitized fMRI techniques. During each vascular challenge BOLD and CBF signals were determined simultaneously with a combined BOLD and flow-sensitive alternating inversion recovery (FAIR) pulse sequence. There was a good correlation between the global BOLD signal intensity changes during breath holding and CO(2) inhalation supporting the notion that the BHT is equivalent to CO(2) inhalation in evaluating the hemodynamic reserve capacity with BOLD fMRI. In contrast, there was no correlation between relative CBF changes during both vascular challenges, which was probably due to the reduced temporal resolution of the combined BOLD and FAIR pulse sequence.

Adult↗
PubMed2000

MRI of disseminated developmental dysmyelination in Fukuyama type of CMD.

Whether the pathologic origin of white matter lesions in Fukuyama type of congenital muscular dystrophy (FCMD) is delayed myelination or dysmyelination is a controversial issue. This study investigated pathologic distribution in white matter with heavily T(2)-weighted images using fluid-attenuated inversion recovery (FLAIR) pulse sequence. For detection of abnormal white matter lesions, FLAIR images were approximately twice as sensitive as T(2)-weighted images and five times as sensitive as T(1)-weighted images of spin echo sequence. The distribution of the white matter lesions was disseminated and not correlated with cortical disarrangement. The distribution was not consistent with delayed myelination. These findings support the evidence found using in vitro proton-NMR spectroscopy that the pathologic origin of white matter lesions is dysmyelination. When conventional magnetic resonance imaging is used, masked white matter lesions are easy to misidentify as delayed myelination instead of disseminated developmental dysmyelination. The lesions in the white matter of FCMD are masked because of brain development.

Adolescent↗
PubMed1994

The [(methyloxy)imino]methyl moiety as a bioisoster of aryl. A novel class of completely aliphatic beta-adrenergic receptor antagonists.

Previous studies in the field of beta-adrenergic drugs had supported the hypothesis of the existence of a bioisosterism between the [(methyleneamino)oxy]methyl moiety (C = NOCH2, MAOMM) of type B beta-blocking drugs and the aryl (Ar) of type A beta-blocking agents. In the MAOMM, however, the carbon of the CH2 linked to the oximic oxygen possesses a hybridization (sp3) and a geometry different from those of the corresponding carbon of Ar which possesses an sp2 hybridization. Furthermore, in the MAOMM, in its preferred conformation, the unsaturated portion (C = N) is situated in a spatial area which does not correspond exactly to the area occupied by Ar. The formal inversion of the atomic sequence C = NOCH2 of the MAOMM leads to a different type of group, the [(methyloxy)imino]methyl moiety (CH2ON = C, MOIMM), which, in the E configuration, appears to present greater steric and electronic analogies with an Ar, with respect to the MAOMM. On the basis of these observations, some completely aliphatic (E)-N-(3-amino-2- hydroxypropylidene)(alkyloxy)amino derivatives of type C (11a,b and 12a, b) were synthesized, the their beta-adrenergic properties were compared with those of the corresponding [(methyleneamino)oxy]-methyl isomers of type B (19a, b and 20a, b). The similar beta-adrenergic properties of 11, 12 and 19, 20 evaluated in vitro both by radioligand binding assays and by functional tests on isolated preparations, are discussed on the basis of considerations regarding the spatial correspondences and electronic analogies between the MOIMM and the MAOMM.

Adrenergic beta-1 Receptor Antagonists↗
PubMed2006

Genome assembly comparison identifies structural variants in the human genome.

Numerous types of DNA variation exist, ranging from SNPs to larger structural alterations such as copy number variants (CNVs) and inversions. Alignment of DNA sequence from different sources has been used to identify SNPs and intermediate-sized variants (ISVs). However, only a small proportion of total heterogeneity is characterized, and little is known of the characteristics of most smaller-sized (<50 kb) variants. Here we show that genome assembly comparison is a robust approach for identification of all classes of genetic variation. Through comparison of two human assemblies (Celera's R27c compilation and the Build 35 reference sequence), we identified megabases of sequence (in the form of 13,534 putative non-SNP events) that were absent, inverted or polymorphic in one assembly. Database comparison and laboratory experimentation further demonstrated overlap or validation for 240 variable regions and confirmed >1.5 million SNPs. Some differences were simple insertions and deletions, but in regions containing CNVs, segmental duplication and repetitive DNA, they were more complex. Our results uncover substantial undescribed variation in humans, highlighting the need for comprehensive annotation strategies to fully interpret genome scanning and personalized sequencing projects.

Base Sequence↗
PubMed2001

Efficient expression of foreign genes in human CD34(+) hematopoietic precursor cells using electroporation.

Introduction of foreign genes into human CD34(+) hematopoietic precursor cells offers a means to correct inborn errors or to protect human stem cells from chemotherapeutic damage. Electroporation is a non-chemical, nonviral, highly reproducible means to introduce foreign genes into mammalian cells that has been used primarily for rapidly dividing cells. CD34(+) cells isolated from mobilized peripheral blood of patients were cultured for 48 h in serum-free culture medium supplemented with Flt-3 ligand, stem cell factor and thrombopoietin. Cell cycle analysis showed an increase in % S-phase from 2% on day 0 to 28% on day 2 without significant loss of mean fluorescence intensity (MFI). Optimal electroporation conditions for CD34(+) cells were 550 V/cm, 38 ms, 30 microg DNA/500 microl at cell densities between 0.2 x 10(6) and 10 x 10(6) cells/ml resulting in transient EGFP gene expression in 21% (+/- 1%) of CD34(+) precursor cells, as determined by flow cytometry 48 h after electroporation. The more primitive cells were also found to be EGFP(+) as determined by subset analysis using Thy1, CD38, AC133 and c-kit conjugated monoclonal antibodies. Methylcellulose assays on electroporated CD34(+) cells yielded 20% (+/- 7%) EGFP(+) colonies (CFU-GM, BFU-E and CFU-mix) and 22% (+/- 5%) EGFP(+) long-term colony-initiating cells (LTC-IC). The reporter gene was found to be integrated into the LTC-IC genomic DNA as determined by inverse PCR and DNA sequencing. These results suggest that electroporation has the potential to effectively and stably deliver exogenous genes into human hematopoietic precursor cells.

Antigens, CD34↗
PubMed2003

Super acidifiers: the origin of the exceptional electron transmission capability of the SO2CF3 group in carbanion stabilization.

As part of studies aimed at clarifying conflicting reports concerning the acidifying effects exerted by the SO2CF3 vs. NO2 moieties with respect to carbanion stabilities, we have investigated the ionization equilibria of an extended set of benzyltriflones and have determined both pKa values of the carbon acids and 1H and 13C NMR parameters of the resulting carbanions. Acidities determined in H2O-Me2SO mixtures and in pure Me2SO show a contrasting behaviour between 4-X-substituted benzyl triflones and related arylnitromethanes. While the latter exhibit a decreasing acidity on going from H2O to Me2SO media, the benzyltriflone analogues show in fact increasing acidity in Me2SO. This opposing trend suggests that the exocyclic alpha-SO2CF3 moiety is strongly stabilizing the negative charge of the carbanions through polarizability effects favored by the dipolar aprotic Me2SO solvent. As a result, inversions in the acidity sequences of alpha-NO2 and alpha-SO2CF3 activated carbon acids are observed on going from H2O to Me2SO. 1H and 13C NMR data are in full accord with the conclusion that only little negative charge is transferred to the 4-X-substituted phenyl ring upon ionization. Increasing further the ring substitution by electronegative groups to 2,4- and 2,4,6- patterns, enhances the charge transfer but this nevertheless remains moderate even with the most activated 2,4,6- trinitro or 2,6-dinitro-4-SO2CF3 sequences. Altogether, our results provide convincing evidence of the unusual electron transmission ability of the very strongly acidifying SO2CF3 group.

Journal Article↗
PubMed2003

A topographical study of mechanical and electrical properties of single myocytes isolated from normal guinea-pig ventricular muscle.

Major regional differences in the electrical properties of myocytes from ventricular muscle have been described previously, on the basis of samples taken from a maximum of three regions in each heart. In order to define the topographical basis for such differences, we studied the electrical and mechanical properties of single myocytes isolated from 20 regions throughout the ventricles in the normal guinea-pig heart. Single myocytes were isolated using an enzymatic dispersion method, and were studied under conditions that were close to physiological. Cell capacitance and action potentials were recorded using the switch-clamp technique, and cell length and evoked shortening were measured using a photodiode array system. In the left ventricular free wall, mid-myocardial cells were longer and had greater capacitative surface area than surface myocytes. There were transmural but not longitudinal differences in APD90 (action potential duration to 90% repolarization), with the longest APD90 in subendocardial and the shortest in subepicardial myocytes. We found a septum-left ventricular free wall-right ventricular free wall gradient, with the longest APD90 in the septum and the shortest in the right ventricular free wall. The regional distribution of APD90 was closely mirrored by relaxation time. Peak cell shortening was greater in subendocardial myocytes than in subepicardial myocytes in the left ventricular free wall, and in myocytes from the left side of the septum compared with the right. We concluded that the regional distribution of APD is closely and inversely related to the sequence of ventricular depolarization, and that the regional variations in cell shortening amplitude are related principally to reported regional variations in wall stress.

Action Potentials↗
PubMed2004

Single-molecule study of RuvAB-mediated Holliday-junction migration.

Branch migration of Holliday junctions is an important step of genetic recombination and DNA repair. In Escherichia coli, this process is driven by the RuvAB complex acting as a molecular motor. Using magnetic tweezers, we studied the RuvAB-directed migration of individual Holliday junctions formed between two approximately 6-kb DNA molecules of identical sequence, and we measured the migration rate at 37 degrees C and 1 mM ATP. We directly demonstrate that RuvAB is a highly processive DNA motor protein that is able to drive continuous and unidirectional branch migration of Holliday junctions at a well defined average speed over several kilobases through homologous sequences. We observed directional inversions of the migration at the DNA molecule boundaries leading to forth-and-back migration of the branch point and allowing us to measure the migration rate in the presence of negative or positive loads. The average migration rate at zero load was found to be approximately 43 bp/sec. Furthermore, the load dependence of the migration rate is small, within the force range of -3.4 pN (hindering force) to +3.4 pN (assisting force).

Bacterial Proteins↗
PubMed1977

Physical mapping of a DNA sequence common to plasmids of incompatibility group F I.

We have mapped a region of homology within a 2.2 kilobase segment of plasmids of incompatibility group F I, WHICH IS CONTAINED IN AN EcoRI restriction enzyme fragment bearing genes for autonomous replication; The coordinates of the 2.2 kilobase segment are 46.4F-48.6F on the physical map of the F plasmid. The orgin of vegetative replication has been mapped at 42.5F, at which site F has no sequence homology with other group F I plasmids. Plasmids belonging to other incompatibility groups have no homology with the 46.4-48.6 F segment. Possible mechanisms underlying incompatibility are discussed. We think that incompatibility is due to either a limitation in a common equipartitioning mechanism or a limitation in a common replication control. In either case, the common mechanism is specific for plasmids belonging to a given incompatibility group.

Base Sequence↗
PubMed1985

An invertible element of DNA controls phase variation of type 1 fimbriae of Escherichia coli.

The expression of type 1 fimbriae (pili) of Escherichia coli is turned on and off at the transcriptional level at a high frequency (10(-3) per cell per generation) in a process termed phase variation. Using Southern blot and DNA sequence analysis, we have detected a genomic rearrangement in the switch region immediately upstream of the fimbrial structural gene. This rearrangement involves an invertible 314-base-pair segment of DNA whose alternating orientation apparently results in the on-and-off activation of a promoter that determines the state of fimbrial expression.

Base Sequence↗