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PubMed2000

1999 ARRS Executive Council Award. Contrast-enhanced CT of small hypovascular hepatic tumors: effect of lesion enhancement on conspicuity in rabbits. American Roentgen Ray Society.

OBJECTIVE: The purpose of this study was to evaluate the effect of lesion enhancement on the conspicuity of small hypovascular hepatic tumors in an animal model. MATERIALS AND METHODS: Seven VX2 hepatic tumors in five rabbits were imaged. Dynamic contrast-enhanced CT was performed at a single level centered over the lesions at 5-sec intervals for 119 sec after injection of 2 ml/kg i.v. contrast material at 2 ml/sec. Attenuation was measured over time within regions of interest in the tumor and normal liver, aorta, inferior vena cava, and portal vein. Lesion conspicuity, defined as the difference between the attenuation of the uninvolved liver and neoplasm, was calculated. RESULTS: The mean diameter of the tumors on CT was 10 mm (range, 6-15 mm). The tumors appeared as low-attenuation lesions with progressive enhancement during the arterial phase and early portal phase. Peak mean lesion attenuation was 60 +/- 27 H (enhancement, 23 H) at 64 sec. Peak mean lesion conspicuity was 80 +/- 18 H at 39 sec, occurring 10 sec before the peak mean hepatic attenuation of 135 +/- 15 H (enhancement, 67 H) at 49 sec. Relative lesion conspicuity paralleled relative enhancement of the liver throughout the imaging period. CONCLUSION: Although low-level tumor enhancement during the arterial phase and early portal phase reduced the conspicuity of small hypovascular tumors in this animal model, our results support the use of maximum liver enhancement as a marker for peak lesion conspicuity.

Animals↗

PubMed2000

Fingerprint enhancement revisited and the effects of blood enhancement chemicals on subsequent profiler Plus fluorescent short tandem repeat DNA analysis of fresh and aged bloody fingerprints.

This study was aimed at determining the effect of seven blood enhancement reagents on the subsequent Profiler Plus fluorescent STR DNA analysis of fresh or aged bloody fingerprints deposited on various porous and nonporous surfaces. Amido Black, Crowle's Double Stain. 1,8-diazafluoren-9-one (DFO), Hungarian Red, leucomalachite green, luminol and ninhydrin were tested on linoleum, glass, metal, wood (pine, painted white), clothing (85% polyester/15% cotton, 65% polyester/35% cotton, and blue denim) and paper (Scott 2-ply and Xerox-grade). Preliminary experiments were designed to determine the optimal blood dilutions to use to ensure a DNA typing result following chemical enhancement. A 1:200 blood dilution deposited on linoleum and enhanced with Crowle's Double Stain generated enough DNA for one to two rounds of Profiler Plus PCR amplification. A comparative study of the DNA yields before and after treatment indicated that the quantity of DNA recovered from bloody fingerprints following enhancement was reduced by a factor of 2 to 12. Such a reduction in the DNA yields could potentially compromise DNA typing analysis in the case of small stains. The blood enhancement chemicals selected were also evaluated for their capability to reveal bloodmarks on the various porous and nonporous surfaces chosen in this study. Luminol. Amido Black and Crowle's Double Stain showed the highest sensitivity of all seven chemicals tested and revealed highly diluted (1:200) bloody fingerprints. Both luminol and Amido Black produced excellent results on both porous and nonporous surfaces, but Crowle's Double Stain failed to produce any results on porous substrates. Hungarian Red, DFO, leucomalachite green and ninhydrin showed lower sensitivities. Enhancement of bloodmarks using any of the chemicals selected, and short-term exposure to these same chemicals (i.e., less than 54 days), had no adverse effects on the PCR amplification of the nine STR systems surveyed (D3S 1358, HumvWA, HumFGA, D8S1179, D21S11, D18S51, D5S818, D13S317, D7S820) or of the gender determination marker Amelogenin. The intensity of the fluorescent signals was very similar and the allele size measurements remained constant and identical to those of untreated bloody fingerprints. No additional background fluorescence was noted. Continuous exposure (for 54 days) to two of the seven enhancement chemicals selected (i.e., Crowle's Double Stain and Hungarian Red) slightly reduced the amplification efficiency of the longer STR loci in profiles of fresh and 7 to 14-day-old bloodprints. This suggests that long-term exposure to these chemicals possibly affects the integrity of the DNA molecules. This study indicates that significant evidence can be obtained from fresh or aged bloody fingerprints applied to a variety of absorbent and nonabsorbent surfaces which are exposed to different enhancement chemicals for short or long periods of time. It also reaffirms that PCR STR DNA typing procedures are robust and provide excellent results when used in concert with fluorescence-based detection assays after fingerprint identification has taken place.

Blood Chemical Analysis↗

PubMed1985

DNA-mediated gene transfer efficiency is enhanced by ionizing and ultraviolet irradiation of rodent cells in vitro. I. Kinetics of enhancement.

The enhancement effects of ionizing and ultraviolet radiation on the efficiency of DNA-mediated gene transfer were studied. The established cell line, Rat-2, consists of cells that are density-dependent contact-inhibited and produce flat monolayers in vitro. When these cells are infected with SV40 virus, a small fraction of cells becomes morphologically "transformed" due to the stable expression of the viral A-gene. Rat-2 cells are competent for DNA-mediated gene transfer, deficient in thymidine kinase activity (TK-), and will die in HAT selective media. Confluent Rat-2 cells were transfected with purified SV40 viral DNA (via calcium phosphate precipitation), irradiated with either X rays or ultraviolet, trypsinized, plated, and assayed for the formation of foci on Rat-2 monolayers. Both ionizing and ultraviolet radiation enhanced the frequency of A-gene transformants/survivor compared to unirradiated transfected cells. These enhancements were nonlinear and dose dependent. A recombinant plasmid, pOT-TK5, was constructed that contained the SV40 virus A-gene and the Herpes Simplex virus (HSV) thymidine kinase (TK) gene. Confluent Rat-2 cells transfected with pOT-TK5 DNA and then immediately irradiated with either X rays or 330 MeV/amu argon particles at the Berkeley BEVALAC showed a higher frequency of HAT+ colonies/survivor than unirradiated transfected cells. In both cases the enhancement contained a linear and a higher order component in dose, but the argon ions were at least twice more efficient than X rays in producing enhancement per unit dose. Rat-2 cells transfected with pOT-TK5, X-irradiated, and assayed for either TK transformation or A-gene transformation showed the same dose dependence for radiation enhancement. Rat-2 cells transfected with the plasmid, pTK2, containing only the HSV TK-gene were enhanced for TK transformation by both X rays and ultraviolet radiation. SV40 A-gene products are not necessary for the radiation enhancement of the efficiency of gene transfer. This in vitro system will be used to study the lesions produced by ionizing radiation on mammalian cell DNA that may act as substrates for integration of exogenously introduced plasmid DNA.

Animals↗

PubMedDate not supplied

Ophthalmoplegic migraine: reversible enhancement and thickening of the cisternal segment of the oculomotor nerve on contrast-enhanced MR images.

BACKGROUND AND PURPOSE: Ophthalmoplegic migraine is a rare condition characterized by the association of headaches and an oculomotor nerve palsy. We report six patients with typical clinical features of this disorder in whom enhancement of the cisternal segment of the oculomotor nerve developed during the acute phase, followed by resolution of enhancement over several weeks as the symptoms resolved. METHODS: Six patients, ages 3 to 27 years, underwent MR imaging during the acute phase of ophthalmoplegic migraine and at the time of recovery several weeks later. The MR studies, performed on a 1.5-T MR unit, included noncontrast and contrast-enhanced axial and coronal T1-weighted sequences. Sagittal images were obtained in two patients, with and without contrast enhancement. RESULTS: Enhancement of the cisternal segment of the oculomotor nerve was seen in all patients at initial presentation. Contrast-enhanced studies also showed focal thickening at the exit of the nerve in the interpeduncular cistern in five of six patients. No patient had enhancement of the cavernous sinus or adjacent dura. Enhancement was almost completely resolved on follow-up studies 7 to 9 weeks later. CONCLUSION: Our findings confirm an intrinsic transient abnormality in the cisternal segment of the third nerve in patients with a typical clinical presentation of ophthalmoplegic migraine.

Adolescent↗

PubMed1997

Diagnosis of liver metastases from colorectal adenocarcinoma. Comparison of spiral-CTAP combined with intravenous contrast-enhanced spiral-CT and SPIO-enhanced MR combined with plain MR imaging.

PURPOSE: The purpose of this study was to determine whether MR with and without SPIO (AMI-25) could replace spiral-CTAP in the staging of colorectal adenocarcinoma. MATERIAL AND METHODS: Thirty-five patients were studied prospectively by means of i.v. contrast-enhanced spiral-CT, spiral-CTAP, and MR of the liver. MR imaging was performed before and after infusion of AMI-25. Diagnoses were compared to intraoperative findings (n = 35) which included intraoperative ultrasound (n = 21), and follow-up CT (n = 18). RESULTS AND CONCLUSION: Fifteen patients were found to have a total number of 53 liver metastases and 43 benign lesions were detected. Evaluation was performed in four different ways: 1) i.v. contrast-enhanced spiral-CT; 2) i.v. contrast-enhanced spiral-CT + spiral-CTAP; 3) plain MR; 4) plain MR + SPIO-enhanced MR. I.v. contrast-enhanced spiral-CT, spiral-CTAP and SPIO-enhanced MR identified patients with liver metastases with equal sensitivity. However, owing to its significantly higher sensitivity, based on a lesion-by-lesion analysis, spiral-CTAP cannot be replaced by SPIO-enhanced MR in patients who are to undergo liver resection. A limitation in spiral-CTAP is its relatively low specificity.

Adenocarcinoma↗

PubMed2005

Clinical management of hepatic malignancies: ferucarbotran-enhanced magnetic resonance imaging versus contrast-enhanced spiral computed tomography.

This study compares ferucarbotran-enhanced magnetic resonance (MR) imaging with spiral computed tomography (CT) in the clinical management of patients with suspected hepatic malignancy. One hundred fifty-nine patients with suspected liver malignancy were included in a prospective, multicenter, phase IIIB clinical trial. Patients were examined with baseline plus contrast-enhanced spiral CT and with baseline plus ferucarbotran-enhanced MR imaging. For each patient, four maps of liver lesions were constructed by a trusted blind party on the basis of (a) baseline plus contrast-enhanced spiral CT, (b) baseline MR imaging, (c) baseline plus ferucarbotran-enhanced MR imaging, and (d) final diagnosis. Three blinded experts evaluated the treatment options for each map. The concordance of the treatment choice based on imaging with the treatment choice based on final diagnosis was verified. The final therapeutic decision was radical therapy for 85 patients, palliative therapy for 49 patients, and no treatment for 25 patients who had a final diagnosis of benign lesion. Proper treatment allocation was achieved in 121 (76%) of 159 patients when the evaluation was based on liver maps obtained from spiral CT, in 97 (61%) of 159 patients when the evaluation was based on liver maps obtained from baseline MR imaging, and in 136 (85%) of 159 patients when the evaluation was based on liver maps obtained from baseline plus ferucarbotran-enhanced MR imaging. MR imaging with ferucabotran was significantly superior to spiral CT for correct treatment allocation (P = 0.0167). Ferucarbotran-enhanced MR imaging is superior to spiral CT in clinical management of patients with suspected hepatic malignancy.

Adult↗

PubMed1986

SV40 enhancer-binding factors are required at the establishment but not the maintenance step of enhancer-dependent transcriptional activation.

We have used temperature-sensitive COS cells to design delayed competition experiments in which competition for simian virus 40 (SV40) enhancer factors occurs after enhancer-dependent transcription has been established. The results demonstrate that competition for SV40 enhancer-binding factors has no effect on enhancer-dependent transcription after transcription has been established at the SV40 early promoter. These data show that the enhancer and factors that bind to it are involved in the establishment of stable transcription complexes, although they do not show whether enhancer factors are an integral part of the transcription complexes. Furthermore, the results of delayed competition experiments with a replicating test plasmid are consistent with the possibility that enhancer-dependent stable transcription complexes could be maintained after DNA replication.

Binding, Competitive↗

PubMed1992

The Mu transpositional enhancer can function in trans: requirement of the enhancer for synapsis but not strand cleavage.

The phage Mu transpositional enhancer has been previously shown to stimulate the initial rate of the Mu DNA strand transfer reaction by a factor of 100. We now show that the Mu enhancer can function in trans on an unlinked DNA molecule. This activity is greatly facilitated by the presence of a free DNA end proximal to the enhancer element. Function of the enhancer in trans does not alter either the requirement for donor DNA supercoiling or for the two Mu ends to be in their proper orientation on the donor plasmid. An important consequence of these findings is that we have been able to evaluate directly the step in the transposition reaction for which the enhancer is required. We show that the role of the enhancer is limited to promoting productive synapsis; efficient strand cleavage can occur in the absence of the enhancer.

Bacteriophage mu↗

PubMed2006

Enhancement kinetics of normal ovaries on dynamic contrast-enhanced MR imaging.

OBJECTIVE: The objective was to determine the enhancement kinetics of the normal ovaries in healthy women on dynamic contrast-enhanced magnetic resonance (DCE-MR) imaging. METHOD: Twenty-one women who had normal ovulatory cycles (volunteers; mean age=26.3 years, range=20-35), normal hormone profile, and apparently normal ovaries on ultrasonographic scan underwent DCE-MR imaging on a 1.5-T system (Philips Medical Systems, Gyroscan Intera, Best, The Netherlands) using a phased array pelvic coil. Sequential images with an imaging time of 14.4s per dynamic image were acquired before and after injection of a contrast bolus at 30s and at 1, 2, 3, 4, and 5 min. On postprocessing examination the following measurements were obtained for ovarian and muscle tissue: the signal intensity value per dynamic study, early phase enhancement rate, time to peak enhancement (Tp), and percentage of wash-out at the fifth minute were determined. Data of the ovaries and skeletal muscle were compared using Wilcoxon's rank sum test. RESULTS: Most of the mean values of the postcontrast signal intensity measurements, the mean values of the early phase enhancement rate, and the percentage of wash-out at the fifth minute were found to be significantly higher in ovary than in muscle (p<0.05). The mean values of Tp, on the other hand, were nonsignificantly lower in ovary than in muscle (p>0.05). On the examination of the mean signal intensity-time data graphics the ovary showed a tendency toward greater and quicker enhancement and wash-out. CONCLUSION: In our opinion, DCE-MR imaging, which determines contrast enhancement such as wash-in and wash-out kinetics, can provide knowledge of ovarian vascularization. Thus, by using DCE-MR imaging, determination of these vascularization changes in various ovarian diseases may provide us with additional parameters in the diagnosis of and treatment strategies for ovarian diseases.

Adult↗

PubMed2000

Enhancement pattern of normal extraocular muscles in dynamic contrast-enhanced MR imaging with fat suppression.

PURPOSE: To evaluate the internal structure of normal extraocular muscles on fat-suppressed dynamic contrast-enhanced MR imaging. MATERIAL AND METHODS: Ten subjects were examined using fat-suppressed dynamic contrast-enhanced MR imaging. We evaluated the enhancement pattern (C-shaped or ring-like) of extraocular muscles and quantified the maximum ratios of enhancement (Rmax) and maximum ratios of signal increase (Vmax). We also quantified Rmax and Vmax in the central and peripheral portions of medial rectus muscles. RESULTS: In the early phase of dynamic contrast-enhanced MR imaging, a C-shaped or ring-like pattern was observed in 100% of inferior rectus, 95% of medial rectus, 55% of superior rectus, 20% of lateral rectus, and 15% of superior oblique muscles. Overall mean Rmax and Vmax values showed statistically significant differences to the temporal muscles. For the peripheral portion of medial rectus muscles, mean Rmax and Vmax values were greater than for the central portion. CONCLUSION: Using fat-suppressed dynamic contrast-enhanced MR imaging, the C-shape or ring-like internal structure of the extraocular muscles could be visualized, and were considered to reflect their structure of orbital and global layers. Potential usefulness of the fat-suppressed dynamic contrast-enhanced MR imaging for detecting pathological status is suggested.

Adipose Tissue↗

PubMed2006

Mechanism for complement-mediated, antibody-dependent enhancement of human immunodeficiency virus type 1 infection in MT2 cells is enhanced entry through CD4, CD21, and CXCR4 chemokine receptors.

Some antibodies neutralize Human Immunodeficiency Virus (HIV). However, antibody to HIV and complement can enhance HIV replication if cells express both complement receptors and CD4, a phenomenon described as complement-mediated, antibody-dependent enhancement (C'ADE). Although increased binding of opsonized virions has been reported, the mechanism by which C'ADE enhances HIV replication remains unproven. In this study, real-time polymerase chain reaction to detect HIV cDNA indicates that complement and anti-HIV antibodies enhance HIV entry 8- to 30- fold with similar increases in integrated provirus. Thus, complement increases HIV replication through a mechanism of enhanced entry. To further refine the mechanism of C'ADE, chemokine receptor antagonists were employed. JM2987, a CXCR4 chemokine receptor antagonist, blocked HIV infection and C'ADE; thus CD4, complement receptors, and CXCR4 chemokine receptors are required for enhanced entry of HIV into MT2 cells. Finally, anti-HIV immunoglobulin enhanced replication of not only group M clade B HIV but also group M clade D and group O isolates. These data demonstrate that antibodies mediating C'ADE of HIV infection are broadly reactive.

Antibody-Dependent Enhancement↗

PubMed2002

The gypsy insulators flanking yellow enhancers do not form a separate transcriptional domain in Drosophila melanogaster: the enhancers can activate an isolated yellow promoter.

The best-characterized insulator in Drosophila melanogaster is the Su(Hw)-binding region contained within the gypsy retrotransposon. In the y(2) mutant, Su(Hw) protein partially inhibits yellow transcription by blocking the function of transcriptional enhancers located distally from the yellow promoter with respect to gypsy. Previously we have shown that yellow enhancers can overcome inhibition by a downstream insulator in the y(rh1) allele, when a second gypsy element is located upstream of the enhancers. To understand how two insulators neutralize each other, we isolated various deletions that terminate in the regulatory region of the y(rh1) allele. To generate these alleles we used DNA elongation by gene conversion of the truncated chromosomes at the end of the yellow regulatory region. We found that gypsy insulator can function at the end of the truncated chromosome. Addition of the gypsy insulator upstream of the yellow enhancers overcomes the enhancer-blocking activity of the gypsy insulator inserted between the yellow enhancers and promoter. These results suggest that the gypsy insulators do not form separate transcriptional domains that delimit the interactions between enhancers and promoters.

Animals↗

PubMed1985

Xenopus ribosomal gene enhancers function when inserted inside the gene they enhance.

The ribosomal DNA of Xenopus laevis contains repeated sequence elements in the intergenic spacer region that enhance transcription from the adjacent gene promoter (1,2). Previous work has shown that these RNA polymerase I enhancers influence the target promoter when they are in either orientation, at a distance of several kilobases, and only when they are in cis (3-5). In this work, we further show that enhancer activity is unaffected by inserting the enhancers within the transcription unit whose promoter is being enhanced. In addition, enhancer activity does not interfere with transcription through its sequences. The results suggest that the enhancers act at a point prior to the initiation of transcription and that they are likely to be dispensable once transcription has begun.

Animals↗

PubMed1994

One of two Ets-binding sites in the cytokeratin EndoA enhancer is essential for enhancer activity and binds to Ets-2 related proteins.

Expression of the mouse cytokeratin EndoA gene is restricted in endodermal and epithelial cells, and is regulated by an enhancer that is located 1 kilobase (kb) 3' downstream from the gene. The enhancer consists of six direct repeats, of which each contains two predicted Ets binding sites (EBS1 and EBS2) containing GGAA as a core. Mutation analysis showed that EBS1 is essential for the enhancer activity and additional effects of EBS2, suggesting that some Ets-related proteins bind and activate the enhancer through EBS1. We also showed that Ets-2 mRNA is expressed in PYS-2 cells and that Ets-2 protein produced by E. coli interacts with EBS1 but not with EBS2. Using co-transfection assays, we showed that Ets-2 can trans-activate the enhancer in PYS-2 cells. Mutations that impair Ets-2 binding abolished the activity of the EndoA enhancer. The results obtained from the binding competition assay using an Ets-2 specific antibody, however, suggest that EBS1 binds to an Ets protein which is distinct from Ets-2. These data show that Ets-2 related protein binds and activates the EndoA enhancer in a sequence-specific fashion.

Animals↗

PubMed2004

Renal masses: quantitative analysis of enhancement with signal intensity measurements versus qualitative analysis of enhancement with image subtraction for diagnosing malignancy at MR imaging.

PURPOSE: To retrospectively compare quantitative and qualitative methods of assessing magnetic resonance (MR) imaging contrast enhancement as the basis for diagnosing renal malignancy. MATERIALS AND METHODS: MR imaging was performed by using a gadolinium-enhanced breath-hold fat-suppressed three-dimensional T1-weighted gradient-echo sequence in 71 patients (48 men and 23 women; mean age, 62 years; age range, 26-87 years) with 93 renal lesions for which pathologic correlation was available. For quantitative measurements of enhancement, the relative increase in signal intensity values was measured by one investigator with manually defined regions of interest, and the threshold of an increase of 15% or greater was used to distinguish malignant from benign masses. For qualitative assessment, two investigators independently reviewed the subtracted images of all lesions and subjectively determined whether enhancement was present or absent. The sensitivity, specificity, and positive and negative predictive values for each method were calculated and compared. Mean (+/- standard deviation) and median values of relative enhancement were also calculated for benign and malignant lesions. RESULTS: At pathologic analysis, 74 (80%) of the 93 lesions were malignant, and 19 (20%)-including seven oncocytomas-were benign. For diagnosing malignancy based on enhancement alone, sensitivity and specificity, respectively, were 95% (70 of 74 lesions) and 53% (10 of 19 lesions) at quantitative analysis and 99% (73 of 74 lesions) and 58% (11 of 19 lesions) at qualitative analysis. All seven oncocytomas were considered to be malignant with both methods. When the oncocytomas were excluded, specificities increased to 83% (10 of 12 lesions) and 92% (11 of 12 lesions) for the quantitative and qualitative evaluations, respectively. Three of the four malignant lesions incorrectly characterized as benign at quantitative assessment were hyperintense on unenhanced MR images; all were diagnosed correctly at qualitative evaluation. CONCLUSION: Image subtraction enables accurate assessment of renal tumor enhancement, particularly in the setting of masses that are hyperintense on unenhanced MR images.

Adult↗

PubMed1991

Dynamic gadolinium-enhanced MR imaging of the spleen: normal enhancement patterns and evaluation of splenic lesions.

The authors studied the ability to improve detection of splenic lesions during suspended respiration with dynamic gadolinium-enhanced T1-weighted spin-echo magnetic resonance (MR) imaging. In the first phase of the study, normal splenic contrast material enhancement patterns were assessed in 10 control patients without splenic lesions. A heterogeneous signal intensity pattern was observed in 11 patients with splenic lesions during bolus injection of gadopentetate dimeglumine, with conversion to homogeneous enhancement 1 minute later. Mean splenic enhancement was 321% during bolus injection, with a rapid return toward baseline signal intensity thereafter. In the second phase, evaluation of 18 splenic lesions detected with contrast-enhanced computed tomography in 11 patients revealed that dynamic gadolinium-enhanced MR pulse sequences significantly improved lesion conspicuity and detectability compared with conventional T1-and T2-weighted pulse sequences. Contrast-to-artifact ratio measurements were 0.5, 3.7, and 9.3 for conventional T1-weighted, T2-weighted, and dynamic gadolinium-enhanced MR images, respectively.

Adult↗

PubMed2005

Gd-EOB-DTPA enhanced MRI for hepatocellular carcinoma: quantitative evaluation of tumor enhancement in hepatobiliary phase.

OBJECTIVE: The purpose of this study was to evaluate the utility of gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI) for the quantitative evaluation of hepatocellular carcinoma (HCC) and dysplastic nodules in the hepatobiliary phase. MATERIAL AND METHODS: The subjects comprised 12 patients with 27 lesions (22 HCCs and 5 dysplastic nodules). Chemical-shift-selective fat-suppressed T1-weighted sequences were obtained before and 10, 20, and 40 min after the injection of Gd-EOB-DTPA. Quantitative analyses were performed with the enhancement ratio of the lesion and the contrast-to-noise (C/N) ratio. RESULTS: The enhancement ratios of the HCCs were 44.0+/-36.5, 44.7+/-46.8, and 47.7+/-52.8 (%) at 10, 20, and 40 min, respectively, after the injection of Gd-EOB-DTPA. The enhancement ratios of the dysplastic nodules were 36.2+/-34.3, 44.3+/-37.3, and 40.1+/-46.8 (%). The C/N ratios of the HCCs were 0.2+/-6.6 for the precontrast image, and -9.2+/-12.6, -9.9+/-14.8, and -12.7+/-15.7 at 10, 20, and 40 min, respectively, after the injection of Gd-EOB-DTPA. The C/N ratios of the dysplastic nodules were 1.4+/-8.0, -13.7+/-11.1, -13.3+/-7.6, and -13.1+/-10.4. No significant differences were found between the HCCs and the dysplastic nodules in the enhancement ratio and the C/N ratio. Only two HCCs showed a positive C/N ratio value, and these HCCs were pathologically confirmed to be a well differentiated and a moderately differentiated carcinoma, respectively. CONCLUSION: HCCs and some of the dysplastic nodules showed hypointensity in the hepatobiliary phase in Gd-EOB-DTPA-enhanced MRI. No specific enhancement was observed, regardless of tumor differentiation.

Aged↗

PubMed1991

Every enhancer works with every promoter for all the combinations tested: could new regulatory pathways evolve by enhancer shuffling?

The promoters and enhancers of cell type-specific genes are often conserved in evolution, and hence one might expect that a given enhancer has evolved to work best with its own promoter. While this expectation may be realized in some cases, we have not found evidence for it. A total of 27 combinations of different promoters and enhancers were tested by transfection into cultured cells. We found that the relative efficiency of the enhancers is approximately the same, irrespective of the type of promoter used, i.e., there was no strong preference for any given enhancer/promoter combination. Notably, we do not see particularly strong transcription when the immunoglobulin kappa enhancer (or the immunoglobulin heavy chain enhancer) is used to activate a kappa gene promoter. We propose that a generally permissive enhancer/promoter interaction is of evolutionary benefit for higher eukaryotes: by enhancer shuffling, genes could be easily brought under a new type of inducibility/cell type specificity.

B-Lymphocytes↗