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PubMed1991

The yeast rRNA gene enhancer does not function by recycling RNA polymerase I and cannot act as a UAS.

The mechanism of action of the yeast rRNA gene enhancer was investigated by measuring transcription of an rRNA minigene, cloned into a multicopy plasmid, in transformed yeast. Expression of the minigene was increased when the enhancer was cloned either upstream of or downstream from the minigene. When an enhancer was present both upstream and downstream of the minigene, the upstream element was functionally dominant. The upstream enhancer was active in this construct in the absence of detectable read-through by any RNA polymerase. In a construct containing tandem rRNA minigenes, an enhancer element located between the two promoters activated transcription from both independently. Therefore, the enhancer does not appear to activate transcription by recycling RNA polymerase I molecules to the promoter. The enhancer also failed to activate transcription from the intact promoter of the yeast CYC1 gene, and was unable to functionally substitute for the natural upstream activation sequences (UASs) of this gene. Therefore, the enhancer functions differently to UASs of RNA polymerase II genes, and is probably polymerase-specific.

Blotting, Northern↗

PubMed1987

Magnetic resonance imaging of human cerebral infarction: enhancement with Gd-DTPA.

Five patients (1 female and 4 males) with cerebral infarction of 4 h to 27 months duration were studied 9 times with magnetic resonance (MR) using Gd-DTPA. Spin-echo (SE) MR images (MRI) were obtained before and after the administration of Gd-DTPA, and correlative CT scans were performed on the same day. In 2 cases, 4 h and 27 months after the ictus, there was no enhancement with Gd-DTPA. There was faint enhancement in 2 cases with cerebral infarction of about 24 h duration and obvious enhancement in all cases in the subacute stage. Compared with enhanced CT, MR using Gd-DTPA demonstrated more obvious enhancement of infarcted areas. MR enhancement using Gd-DTPA showed a gradual increase and the accumulated Gd-DTPA in infarcted areas slowly diffused to the periphery. MR enhancement with Gd-DTPA is similar to that of enhanced CT, but may be more sensitive in the detection of blood brain barrier breakdown.

Adult↗

PubMed1980

Contrast enhancement in ischaemic lesions. I. Relationship to prognosis.

The contribution of post-enhancement CT scans to the diagnosis of acute cerebral infarction was studied in a consecutive series of infarcts. The timing, density and pattern of enhancement were also analysed for any possible prognostic information, and the incidence of factors of known prognostic significance was estimated on plain and contrast enhanced scans. Enhancement patterns of infarcts were variable and in those cases in which the plain CT diagnosis was equivocal the post-enhancement CT was not infrequently ambiguous also, and occasionally misleading. The outcome of infarcts that enhanced was significantly poorer than in those not showing enhancement, although no relationship between the timing, density or pattern of enhancement and prognosis could be shown. Consideration of the distribution of other factors known to adversely affect prognosis in the two groups does not adequately account for the difference between them suggesting that the contrast medium itself could be the cause of the poorer outcome. There are few positive indications for post-contrast scanning of suspected infarcts and the possible adverse effects of contrast medium should be considered prior to administration.

Brain Ischemia↗

PubMed1984

A new method for the diagnosis of acute hemorrhagic-necrotizing pancreatitis using contrast-enhanced CT.

Twenty-eight consecutive patients with a first attack of alcohol-induced pancreatitis were studied using contrast-enhanced CT. The findings on CT were then related to the course of the disease. The patients with acute hemorrhagic-necrotizing pancreatitis showed significantly lower enhancement values of the pancreatic parenchyma than those with milder forms of the disease. The next 20 patients with severe pancreatitis were scanned using a slightly modified procedure. The enhancement values were calculated and plotted on the graphs for the 2 former groups. Two categories of pancreatic enhancement were found: "low enhancement" and "high enhancement." In all 10 patients with "low-enhancement" values surgery revealed hemorrhagic-necrotizing pancreatitis. In the 10 patients with "high-enhancement" values conservative treatment was continued, and the clinical course was nonfulminant in all of them.

Acute Disease↗

PubMed1998

Hydrogen peroxide-enhanced transanal ultrasound in the assessment of fistula-in-ano.

UNLABELLED: Appropriate classification of the fistulous tracts in patients with fistula-in-ano may be of value for the planning of proper surgery. Conventional transanal ultrasound has limited value in the visualization of fistulous tracts and their internal openings. Hydrogen peroxide can be used as a contrast medium for ultrasound to improve visualization of fistulas. PURPOSE: This prospective study evaluates hydrogen peroxide-enhanced ultrasound in comparison with physical examination, standard ultrasound, and surgery in the assessment of fistula-in-ano. METHODS: Twenty-one consecutive patients (4 women; mean age, 42 years) with fistula-in-ano were evaluated by local physical examination (inspection, probing, and digital examination), conventional ultrasound, and hydrogen peroxide-enhanced ultrasound before surgery. Ultrasound was performed using a B&K Diagnostic Ultrasound System with a 7-MHz rotating endoprobe. Hydrogen peroxide (3%) was infused via a small catheter into the fistula. The results of physical examination, ultrasound, and hydrogen peroxide-enhanced ultrasound were compared with surgical data as the criterion standard. The additive value of standard ultrasound and hydrogen peroxide-enhanced ultrasound compared with physical examination was also determined. RESULTS: At surgery, 8 intersphincteric and 11 transsphincteric fistulas and 2 sinus tracts (without an internal opening) were found. During physical examination, probing was incomplete in 13 patients, the diagnosis being correct in the other 8 patients (38%) as a low (intersphincteric or transsphincteric) fistula. With conventional ultrasound, the assessment of fistula-in-ano was correct in 13 patients (62%); defects in one or both sphincters could also be found (n = 8). With hydrogen peroxide-enhanced ultrasound, the fistulous tract was classified correctly in 20 patients, the overall concordance with surgery being 95%. The internal opening was found at physical examination in 15 patients (71%), with hydrogen peroxide-enhanced ultrasound in 10 patients (48%), and during surgery in 19 patients (90%). Secondary extensions, confirmed during surgery, were found in five cases. In two patients, a secondary extension with hydrogen peroxide-enhanced ultrasound was not confirmed during surgery. Both patients developed a recurrent fistula. CONCLUSION: Hydrogen peroxide-enhanced ultrasound is superior to physical examination and standard ultrasound in delineating the anatomic course of perianal fistulas. It makes accurate preoperative assessment of the fistula possible and may be of value for the surgeon in planning therapeutic strategy.

Adult↗

PubMed2005

Epiphyseal and physeal cartilage: normal gadolinium-enhanced MR imaging.

To evaluate the normal appearance of epiphyseal and physeal cartilage on Gadolinium (Gd)-enhanced MR imaging. The appearance and enhancement ratios of 20 proximal and distal femoral epiphyses in 10 normal piglets were analyzed on Gd-enhanced MR images. The correlation of the MR imaging appearance with corresponding histological findings of immature epiphyses was examined. Our results showed that Gd-enhanced MRI could differentiate the differences in enhancement between physeal and epiphyseal cartilage and show vascular canals within the epiphyseal cartilage. Enhanced ratios in the physeal were greater than those in the epiphyseal cartilage (P < 0.005). It is concluded that Gd-enhanced MR imaging reveals epiphyseal vascular canals and shows difference in enhancement of physeal and epiphyseal cartilage.

Animals↗

PubMed1999

MRI of acute cerebral infarcts, increased contrast enhancement with continuous infusion of gadolinium.

We compared contrast enhancement on T1-weighted MRI of acute cerebral infarcts after conventional bolus administration and continuous infusion of gadolinium. We examined 12 patients with a history of acute stroke with contrast-enhanced MRI once a week for a 1 month. Only ischaemic lesions were investigated after cerebral haemorrhage had been excluded by CT. Each MRI study included T2- and proton density-weighted sequences for determination of the size and site of the infarct, immediate postinjection T1-weighted imaging after bolus administration of 0.1 mmol/kg gadolinium-DPTA and delayed T1-weighted imaging after additional continuous infusion of 0.1 mmol/kg over 2 h. A total of 42 MRI studies was performed. In the first week after the onset of stroke, most infarcts (8 of 10) did not enhance after bolus administration, whereas all showed distinct contrast enhancement after the infusion. In the following weeks all but two infarcts showed contrast enhancement after bolus administration; after continuous infusion contrast enhancement could be seen in all cases. While contrast enhancement after bolus administration showed the typical gyriform pattern, enhanced areas were more extensive after the infusion and usually covered the entire infarcted area shown on T2- and proton density-weighted images. We presume that the disturbed blood-brain barrier in ischaemic areas favours delivery of contrast medium to the infarcted tissue if it is offered continuously so that a steady state can develop.

Acute Disease↗

PubMed1996

Gadolinium-enhanced MR imaging of the wrist in rheumatoid arthritis: value of fat suppression pulse sequences.

OBJECTIVE: To determine the usefulness of fat-suppressed gadolinium (Gd)-enhanced MR imaging of the wrist in patients with rheumatoid arthritis (RA). DESIGN AND PATIENTS: Fat-suppressed Gd-enhanced T1-weighted spin-echo (SE) images were obtained and compared with other standard techniques in 38 wrists of 27 patients (22-77 years) with RA. Scoring based on the degree of synovial enhancement of each joint was developed and the total scores (J-score) were correlated with radiographic stage, C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and symptomatic change in the follow-up study. RESULTS: Synovial proliferations showed marked enhancement in all the wrists. In addition, contrast enhancement in the bone marrow and tenosynovium was seen in 36 and eight wrists respectively. Fat-suppressed Gd-enhanced T1-weighted images demonstrated these abnormalities better than other techniques. The J-scores correlated well with values of CRP (P = 0.0034), but not with radiographic stages and ESR. CONCLUSION: Fat-suppressed Gd-enhanced T1-weighted SE images can clearly demonstrate most of the essential lesions in RA including the proliferative synovium, bone erosion, bone marrow inflammatory change, and tenosynovitis. Scoring based on the extent of Gd-enhancement of synovium can be useful in the assessment of the inflammatory status.

Adult↗

PubMed2005

Is there a need for contrast-enhanced T1-weighted MRI of the spine after inconspicuous short tau inversion recovery imaging?

To assess the use of contrast-enhanced T1-weighted images in comparison with short tau inversion recovery (STIR) images for the detection of vertebral bone marrow abnormalities. A total of 201 vertebral magnetic resonance (MR) examinations were included in a prospective trial. Examinations were performed on a 0.5-T MR scanner. The examination protocol included STIR, T2-weighted turbo spin-echo and T1-weighted spin-echo images before and after administration of gadopentetate dimeglumine. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of STIR images were calculated. In the case of abnormal STIR images the additional information from contrast-enhanced images was evaluated using Fisher's exact test. The value of the combined evaluation of STIR and contrast-enhanced T1-weighted images was compared with that of the combined assessment of T2-weighted and contrast-enhanced T1-weighted images. The PPV and the NPV of STIR images for detection of vertebral bone marrow abnormalities were 99.3 and 95.9%. In the case of normal STIR images no relevant additional information was found with contrast-enhanced T1-weighted images, while in the case of abnormal STIR images significant supplementary information was obtained. There was no difference in the diagnostic value when comparing combined assessment of STIR and contrast-enhanced T1-weighted images with combined evaluation of T2-weighted and contrast-enhanced T1-weighted images. Normal STIR images allow contrast-enhanced T1-weighted images for detection of bone marrow abnormalities to be omitted, whereas further imaging is needed in case of abnormal STIR images.

Adult↗

PubMed1998

The pelvis after surgery and radio-chemotherapy for rectal cancer studied with Gd-DTPA-enhanced fast dynamic MR imaging.

The aim of this work was to study the gadolinium-enhancement of malignant and benign pathology in the pelvis after surgery for rectal cancer. Thirty patients with either local recurrence (n = 17) or benign changes related to treatment for rectal cancer (n = 13) were studied with pelvic MR imaging. T2-weighted fast spin-echo as well as T1-weighted spin- or gradient-echo imaging before and after intravenous contrast was performed and referred to as contrast-enhanced MRI (CEMRI). In addition, between the pre- and postcontrast images, dynamic contrast-enhanced MRI (DCEMRI) was performed using a single-slice, multi-phase, contrast-enhanced T1-weighted fast spoiled gradient-echo sequence. The time between the start of contrast injection to the beginning of enhancement, the duration and rate of enhancement as well as enhancement amplitude were recorded. The data were compared with the clinical diagnosis according to biopsy in 8 patients and surgery in 6 patients. In the remaining 16 patients, the clinical diagnosis was obtained by clinical or radiological follow-up. DCEMRI did not improve the diagnostic information compared with CEMRI. None of the examined parameters were found to help discriminating malignant from benign changes. Characterisation of lesions in the pelvis after rectal cancer surgery was not improved by a dynamic gadolinium-enhanced sequence.

Adult↗

PubMed2001

Dynamic contrast-enhanced power Doppler sonography improves the differential diagnosis of liver lesions.

The aim of this paper was to investigate the diagnostic value of dynamic contrast-enhanced power Doppler sonography in the differential diagnosis of liver lesions. We prospectively examined 85 focal liver lesions in 71 patients by real-time gray-scale sonography, power Doppler sonography, and contrast-enhanced power Doppler using two ultrasound contrast agents (Levovist, Optison). Amount and architecture of lesion vascularity and the kinetics of contrast enhancement within the lesions were analyzed. Vascularity was detected in 61% of liver lesions (52/85) by conventional power Doppler, compared to 86% (73/85) by contrast-enhanced power Doppler sonography. Dynamic contrast-enhanced power Doppler identified arterial radial hypervascularity <16 s after contrast injection in 19/22 focal nodular hyperplasias (86%). Irregular hypervascularity was seen with contrast enhancement in the arterial phase in 14/15 hepatocellular carcinomas (93%). In 14/25 hemangiomas (56%), a circular vascularization pattern was noted. Specific lesion diagnosis based on B-scan and conventional and dynamic contrast-enhanced power Doppler sonography led to correct diagnosis in 86% (73/85, 95% confidence interval 78%-94%) compared to 57% (48/85, 95% confidence interval 47%-94%) by B-scan criteria and conventional power Doppler sonography. Contrast-enhanced power Doppler sonography improves diagnostic accuracy in the differential diagnosis of focal liver lesions.

Albumins↗

PubMed2005

Differential diagnosis of nodular lesions in cirrhotic liver by post-vascular phase contrast-enhanced US with Levovist: comparison with superparamagnetic iron oxide magnetic resonance images.

BACKGROUND: We investigated the diagnostic utility of post-vascular phase contrast-enhanced ultrasonography (US) and superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance imaging (MRI) as compared to the histological diagnosis of differential grades of hepatocellular carcinomas (HCCs). METHODS: Forty-nine patients with histologically characterized liver nodules (well-differentiated HCC, n = 20; moderately differentiated HCC, n = 19; poorly differentiated HCC, n = 1; dysplastic nodule, n = 9) received contrast-enhanced US and SPIO-MRI. Subsequently, we quantitatively evaluated the relationships between the images of the nodules and their histological diagnosis and differential grades. RESULTS: The ratio of the echogenicity of the tumorous area to that of the nontumorous area with post-vascular phase contrast-enhanced US (post-vascular phase ratio) decreased as nodules became less differentiated (P < 0.05; Kruskal-Wallis test). The ratio of the intensity of the nontumorous area to that of the tumorous area on SPIO-enhanced MR images (SPIO intensity index) also decreased as nodules became less differentiated (P < 0.01). The post-vascular phase ratio correlated with the SPIO intensity index for HCCs and dysplastic nodules (r = 0.76). The conformity of the result from the post-vascular phase contrast-enhanced US and SPIO-MRI was 96%. CONCLUSIONS: Contrast-enhanced US is a valuable method for predicting the histological grade of HCCs in cirrhotic patients, and may be a good alternative to SPIO-enhanced MRI.

Aged↗

PubMed2001

The role of Gd-enhanced three-dimensional MRI fast low-angle shot (FLASH) in the evaluation of symptomatic lumbosacral nerve roots.

In the field of lumbar spine disorders, three-dimensional (3-D) magnetic resonance imaging (MRI) can clearly depict a lumbar nerve root from the distal region to the dorsal root ganglion. In this study, we used a gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) enhanced-three-dimensional (3-D) fast low-angle shot (FLASH) sequence when examining lumbosacral disorders. The subjects were 33 patients (14 men and 19 women) in whom lumbosacral neural compression had been diagnosed clinically. Twenty-one patients had lumbar disc herniation, 11 had lumbar spinal stenosis, and 1 had lumbar radiculopathy caused by rheumatoid arthritis. Five subjects with low back pain were also studied as a control group. In all patients and in all 5 of the controls, the dorsal root ganglion of every root was enhanced clearly. There was no root enhancement in the 5 controls. Enhancement of the symptomatic nerve roots, caused by compression, was found in 11 of the 33 patients. All 11 patients had radiculopathy, and muscle weakness was more frequent in patients with enhanced nerve roots than in those without enhancement. There was no enhancement of the cauda equina, even in the patients with cauda syndrome. The enhancement effect may reflect some pathological condition of the compressed nerve root and needs to be studied further.

Adolescent↗

PubMed1989

Bent DNA is needed for recombinational enhancer activity in the site-specific recombination system Cin of bacteriophage P1. The role of FIS protein.

A series of recombinational enhancer mutants was constructed by manipulating the ClaI site between the two FIS binding sites of the Hin enhancer. These mutants include insertions from two to 12 base-pairs and two deletions of one or two base-pairs. Recombinational enhancer activity was found only with four mutants carrying either a four base-pair substitution, ten base-pair insertions or a one base-pair deletion, respectively; two other ten base-pair insertion mutants, however, were inactive, although FIS protein binding was unaffected. So, besides binding of FIS protein to its specific sites within the enhancer sequence and the correct helical positioning of these sites on the DNA, another criterion for enhancer activity must be fulfilled. DNA bending assays identify this requirement as a change of the enhancer DNA conformation, which FIS protein is able to induce and to stabilize. This conformational change of the DNA can be blocked by mutations in the central segment between the two FIS binding sites of the Hin enhancer. This sequence has special functions for the recombinational enhancer activity.

Bacteriophages↗

PubMed1991

A key DNA-protein interaction determines the function of the 5'URR enhancer in human papillomavirus type 11.

The 5' end of the upstream regulatory region (URR) of human papillomavirus type 11 (HPV-11) has enhancer function and binds cellular proteins. We have determined that one particular motif, a CCNGTNAC pair, is both necessary and sufficient for enhancer activity. This enhancement of expression can be competed in vivo by concatenated double-stranded oligonucleotides, indicating that protein-DNA binding is a requisite for enhancer activity. A 41-kDa protein, present in all epithelial cells assayed, binds to this enhancer motif. The 5'URR fragment functions as an enhancer both in primary keratinocytes from a variety of body sites and in fibroblasts. We conclude that tissue specificity is not a feature of this enhancer, and that the 41-kDa binding protein is ubiquitous. These data provide evidence that the 5'URR enhancer activity is dependent on only a few sequences and perhaps only one protein.

Amino Acid Sequence↗

PubMed1988

Cooperativity and hierarchical levels of functional organization in the SV40 enhancer.

We have investigated the cell-specific activity of the GT-IIC, GT-I, Sph-II, Sph-I, and octamer motifs of the SV40 enhancer in four cell lines (HeLa cells, MPC11 plasmocytoma B cells, and non-differentiated and retinoic acid-differentiated F9 embryonal carcinoma cells). Our present results reveal the existence of three classes of motifs that interact with cell-specific enhancer factors but that have no enhancer activity of their own: those (class A) that generate enhancer activity following oligomerization of tandem repeats of the motif; those (class B) that cannot enhance transcription when oligomerized as a tandem repeat but whose association with a second motif results in transcription activation after oligomerization; and those (class C) that exhibit enhancer activity when a single copy of the motif is oligomerized. Three levels of functional organization of enhancers can also be defined. The possible implications for enhancer functions are discussed.

Allosteric Regulation↗

PubMed1987

The cis-acting regulatory elements of immunoglobulin heavy chain gene involved in enhanced immunoglobulin production after lipopolysaccharide (LPS) stimulation.

In the present study, the transient expression of the human immunoglobulin heavy chain gene (HIG1) was analyzed in a mouse pre-B-cell line, 70Z/3, after LPS stimulation. HIG1 gene and its recombinant plasmids were transfected by the calcium phosphate method into 70Z/3 cells and the cells were stimulated with lipopolysaccharide (LPS) 48 hr after DNA transfection. The amounts of human heavy chain gene products greatly increased in 70Z/3 cells after LPS stimulation, but the increment was diminished by deletion of the heavy chain gene enhancer element (MluI-HpaI fragment) in the J-C intron from the HIG1 gene. The gene, delta 3, which contained the 5' promoter region and the rearranged VDJ region of HIG1 but lacked the enhancer element, was weakly transcribed in 70Z/3 cells after LPS stimulation. Insertion of the enhancer element into the delta 3 gene greatly enhanced the transcription of the VDJ gene. The highest enhancement of the VH gene transcription rate was obtained when the 3' half of the enhancer element was ligated to the delta 3 gene. The present data suggest that the 3' half of the enhancer element of the heavy chain gene may play an important role in the enhanced production of immunoglobulin which is induced with LPS stimulation.

Animals↗

PubMed1984

Enhancer elements share local homologous twist-angle variations with a helical periodicity.

Several experiments have shown that some enhancers can be exchanged between different genomes. The transferred enhancers were functional (cf. Levinson, B., Khoury, G., Vande Woude, G. and Gruss, P. (1982) Nature 295, 568-572). This argues that these exchanged fragments are recognized as enhancers and possess some common characteristics which other sequences lack. Extensive comparisons of enhancers yielded only very limited nucleotide sequence homology, which appears to be insufficient for enhancer recognition. We suggest that the enhancers located and sequenced to date have recurring, periodic homologous twist-angle (tg) patterns. This helical periodicity and the symmetric nature of the repeating twist-angle features present a recurring spatial geometry. It also offers a possible explanation of the fact that inverted enhancers are still functional. Regions of large twist, roll or main-chain torsion angle delta deviations from regular B-DNA may facilitate enhancer recognition especially when distant from promoter elements. Tissue specificity may be encoded in additional sequence or structural features.

Animals↗