Mechanisms of modulation of the Egr gene family in mammary epithelial cells of different species.

In the adult female, within the estrous cycle, the mammary gland undergoes multiple rounds of growth, with increased cellular proliferation, and involution, with increased apoptosis. The increase in proliferation is elicited by endocrine (Estrogen, Progesterone), as well as locally produced (epidermal growth factor, insulin-like growth factor, etc) growth factors. Among the genes that are modulated during cellular proliferation, immediate early genes play a fundamental role, being rapidly upregulated and then downregulated within the G0/G1 phase of the cell cycle, allowing the progression to the subsequent phases. Egrs (1-4) are immediate early genes that encode for transcription factors that promote, within different cell types and depending on the strength and duration of the stimuli, several different responses like mitogenesis, differentiation, apoptosis or even anti-apoptosis. In this work we have studied the mechanisms of modulation of the Egr family, in mammary epithelial cells of different origin (bovine, canine, feline, murine). Following stimulation with growth medium, Egr mRNA expression showed a strong upregulation reaching a peak at 45-60min, that rapidly declined. Among several cytokines, particularly important for mammary morphogenesis, that we have tested (EGF, IGF-I, insulin, estrogen, progesterone), only EGF upregulated Egrs to levels close to those elicited by growth medium. In order to understand how the Egr transcription factors were regulated, we have inhibited Erk 1/2 and PI3K, molecules that drive two major intracellular signaling pathways. Inhibition of the Erk 1/2 pathway totally abolished Egr upregulation mediated by growth medium or EGF. On the other hand, the PI3K-Akt pathway played a minor role on Egr levels, with a strong inhibitory effect on cat GH2 cells only, that could be ascribed to reduced Erk phosphorylation following PI3K inhibition. Finally we showed that addition of growth medium also upregulated that the mammary luminal marker cytokeratin 18, but only in the murine NMuMG cell line. This is the first manuscript describing how the Egr transcription factors are expressed in mammary epithelial cells of domestic animals and which growth factors and signaling pathways modulate their expression.

Three-dimensional time-of-flight MR angiography in the evaluation of intracranial aneurysms treated with Guglielmi detachable coils.

BACKGROUND AND PURPOSE: Intravascular treatment of intracranial aneurysms is a relatively new therapeutic technique and long-term controlled angiographic trials are needed to assess persistence of aneurysm occlusion. Our purpose was to evaluate the effectiveness of 3D time-of-flight (3D-TOF) MR angiography as a noninvasive screening tool in the follow-up of cerebral aneurysms treated with Guglielmi detachable coils (GDCs). METHODS: Forty-nine patients with 50 intracranial aneurysms previously treated with GDCs were studied with both DSA and 3D-TOF MR angiography. In 14 cases, a second follow-up examination was performed, for a total of 64 aneurysms evaluated. In 25 aneurysms, both pre- and postcontrast MR angiographic studies were obtained. RESULTS: In seven of 64 aneurysms, the MR angiographic studies were considered to be unreliable owing to the presence of artifacts that obscured part of the parent artery and did not allow an accurate evaluation of the aneurysm neck. These seven aneurysms, however, all were shown to be completely occluded at digital subtraction angiography (DSA). In the remaining 57 aneurysms, DSA revealed complete occlusion in 39 and the presence of residual patency in 18, whereas MR angiography showed complete occlusion in 38 and residual patency in 19. Enhanced MR angiography proved to be useful in evaluating residual patency in large and giant aneurysms and in better depicting the distal branch arteries. CONCLUSION: Although artifacts related to the presence of coils are evident on a considerable number of imaging studies, our findings indicate that MR angiography is useful in the evaluation of residual patency of cerebral aneurysms treated with GDCs and may eventually prove valuable in the follow-up of those cases in which a good initial correlation with DSA was demonstrated.

[Comparative assessment of conventional spin echo sequences and turbo spin echo in the study with magnetic resonance of the lesions of the spinal cord]. / Valutazione comparativa fra sequenze SE tradizionali e Turbo SE nello studio con Risonanza Magnetica delle lesioni del midollo spinale.

In the last few years, new magnetic resonance (MR) pulse sequences called Fast or Turbo Spin Echo (TSE) sequences have become available. This kind of T2-weighted images is particularly useful for the study of spondylosis and degenerative spinal conditions, because it both reduces involuntary motion artifacts and its acquisition time is shorter than that of conventional SE T2-weighted images. Our study was aimed at assessing the diagnostic gain of this new type of pulse sequences in intrinsic spinal cord conditions. Therefore, we acquired TSE and conventional SE sequences, consequently, in 36 patients with intrinsic spinal cord conditions, which were apparent on T2-weighted images, and then compared the sensitivity, contrast resolution, and depiction of lesion margins and extent in both acquisition techniques. The results of our study follow: even though all lesions were identified with both techniques, contrast resolution was higher with TSE than with conventional SE images. Lesion margins and extent were substantially equally depicted with both techniques. Finally, TSE sequences had the same, and sometimes even higher, diagnostic yield than conventional SE sequences: therefore, TSE can be considered the sequence of choice in the study of intrinsic spinal cord conditions.

[Magnetic resonance with fat-saturation sequences in studying the upper abdomen: the normal semeiological aspects]. / Risonanza Magnetica con sequenze con saturazione del grasso nello studio dell' addome superiore: aspetti semeiologici normali.

The fat-saturation (FAT-SAT) MR technique decreases the signal intensity of fat in tissues, though yielding the T1, T2 and proton-density (PD) information available on spin-echo (SE) sequences. To investigate the potentials of FAT-SAT sequences in MRI of the upper abdomen, the authors carried out a prospective study including 129 subjects, namely 12 normal volunteers and 117 patients with different abdominal conditions. The patients were submitted to T1-weighted SE sequences (TR 500-600 ms, TE 15 ms), T2W SE (TR 1600-1730 ms, TE 80 ms) and PD SE (TR 1600-1730 ms, TE 20 ms). The images obtained with and without fat suppression were compared both qualitatively and quantitatively, with a special emphasis on the normal anatomy of the upper abdomen: we investigated the efficacy of subcutaneous and retroperitoneal fat suppression (116/129 cases, 90%), the reduction in respiratory and chemical shift artifacts (112/129 cases, 87%) and the better visualization of parenchyma (119/129 cases, 93%) and of other abdominal structures. Concerning the quantitative study, we calculated the signal-to-noise ratio (S/N) for liver, spleen, pancreas, adrenal glands, renal cortex and medulla, the improvement of contrast in these organs after retroperitoneal fat suppression (conspicuity) and the increase in contrast between organs (dynamic range). The statistical analysis showed significant differences between the sequences with and those without fat suppression. Correlations were found between observers' and quantitative evaluations, suggesting that the better yield of FAT-SAT sequences is probably due to three factors: 1) retroperitoneal and subcutaneous fat suppression; 2) increase in S/N ratio for pancreas and renal cortex on T1W images; 3) reduction in the dynamic range of signal intensity, which increases contrast between pancreas, adrenal glands and renal cortex relative to adjacent structures, especially on T2W or PD sequences. The results of this study suggest that FAT-SAT sequences are useful because fat suppression increases contrast and improves image quality, reducing respiratory and chemical shift artifacts.

MR imaging of focal liver lesions: comparison between turbo spin-echo and conventional spin-echo pulse sequences.

The aim of this study was to compare conventional spin-echo (CSE) T2-weighted (T2W) images with turbo spin-echo (TSE) T2W pulse sequences in their ability to detect focal liver lesions. Seventy-eight consecutive patients with focal liver lesions were entered into this study. All patients were imaged using the gradient-echo (GE) sequence with the breath-hold technique for T1-weighted (T1W) images, and CSE and TSE sequences for T2W images. Qualitative evaluation included lesion detection (number of lesions detected) and conspicuity (extent of visualization of lesional borders); quantitative evaluation included the signal-to-noise (S/N) ratio and the contrast-to-noise (C/N) ratio. TSE showed the best performance in terms of lesion detection; however, the difference between TSE and CSE was significant only in the case of benign cysts (p < 0.01). Conspicuity was higher with TSE and CSE, and lower with GE. The S/N and C/N ratios of the two T2W sequences were also comparable, and better than those of GE. However, the combined use of GE and TSE resulted in improved lesion detection. The results show that, because the acquisition time is greatly reduced with TSE sequences, these should be considered as first-line approach to magnetic resonance imaging of the liver for the study of focal lesions.

[An introduction to fast and ultrafast sequences in magnetic resonance]. / Introduzione alle sequenze veloci ed ultraveloci in risonanza magnetica.

The main limitations of magnetic resonance imaging (MRI) are due to the long acquisition time needed for data sampling. Fast and ultrafast sequences, thanks to progress in hardware and software technology, allow the acquisition times to be dramatically reduced. Such improvements will definitely increase MR capabilities and make MRI a fast and dynamic technique no longer depending on patients' cooperation and limited by patients' conditions--e.g., trauma, pediatric, or claustrophobic patients--or even by the anatomic features of the region of interest. The latest experimental studies are aimed at increasing the clinical applications and the perspectives of clinical MRI and at such ambitious goals as MR-fluoroscopy, interventional MRI, total body examination in less than one minute and functional MRI. In this paper the technical principles and the main indications of this new kind of sequences are reported, with a special emphasis on Gradient-Echo (GE), Turbo Spin-Echo (turbo SE) or Fast Spin-Echo (fast SE), Turbo FLASH and Echo Planar (EP) sequence. A smaller flip angle (FA) and the substitution of the 180 degrees RF pulse with a gradient reversal are the main differences of GE from SE sequences. From GE sequences, several fast sequences are derived, such as angiographic and turbo FLASH sequences. The latter, thanks to 180 degrees preinversion RF pulse, using idoneous inversion times (IT), provide flexible contrast. Turbo SE sequences, which are directly derived from conventional SE sequence, allow the acquisition time to be markedly shortened, by acquiring several Fourier lines of K-space for each TR. The repetition of several 180 degrees pulses following the excitatory 90 degrees RF pulse does the trick through the creation of multiple echoes for a single TR. EP sequences are the fastest ones currently available: with them, an image can be acquired in 30-100 ms. However, the limited availability of the relative hardware and the need of both quality implementation and the definition of clinical indications are major obstacles to the widespread use of these sequences. The SE T2-weighted sequence, the main responsible for the long examination time, will be replaced soon. Further implementation of these sequences will make MRI a fast, flexible and adaptable method to any exam and patient disability.

[Turbo-Spin-Echo sequences in focal liver diseases]. / Le sequenze Turbo Spin Echo nelle malattie focali epatiche.

Turbo Spin-Echo (Turbo SE) pulse sequences represent a new type of fast sequences characterized by a dramatic reduction in acquisition time with similar intrinsic contrast to that of conventional Spin-Echo (SE) pulse sequences. For a preliminary clinical comparison of turbo SE and SE sequences, a consecutive series of 25 patients with focal liver lesions was investigated by means of MRI at 1.0 T. The patients were selected on the basis of US or CT positive liver scans for focal lesions. All patients underwent MRI following the same protocol: axial T1-weighted (T1W) gradient echo (GE) sequences (TR/TE = 110/6 ms) with the "breath-hold" technique, T2-weighted (T2W) SE sequences (TR/TE = 1730/90 ms; FL = 60, M = 128 x 256, 2 AC, TA = 7 min 26 sec) and turbo SE sequences (TR/TE = 5100/112 ms, M = 240 x 256, 2 AC, TA = 2 min 48 sec). Slice thickness was 10 mm with a 1-mm gap in all cases. Qualitative (number, size and definition of the lesions) and quantitative (contrast-to-noise ratio (CNR) and relative CNR) variables were considered. SE and turbo SE sequences demonstrated the same number of lesions; the smallest lesion (3 mm) was identified by turbo SE sequences. Turbo SE sequences better depicted lesion margins than SE sequences. In all cystic conditions, CNR was higher in turbo SE than in SE sequences, while it was lower in all the extant conditions. This preliminary experience proves turbo SE pulse sequences to be a valuable tool in liver MRI, which calls for further clinical trials.