Effects of Ovariectomy and Prolactin on Mammary Gland Expressions of Transforming Growth Factor alpha and Epidermal Growth Factor Receptor mRNAs in Mice.

Beginning 15 days after ovariectomy (OVX), a high mammary tumor strain of SHN virgin mice at 3 months of age received subcutaneous injections of danazol (0.5 mug / 0.1 ml olive oil, once a day), perphenazine (0.05 mg / 0.1 ml saline, twice a day) or ovine prolactin (oPRL: 0.25 mg / 0.05 ml buffer, twice a day) for 3 days to modulate their circulating PRL levels. The serum PRL level was significantly decreased by danazol and increased by perphenazine compared to the intact and OVX-control groups. The expression of both transforming growth factor alpha (TGFalpha) mRNA and epidermal growth factor receptor (EGFR) mRNA in the mammary gland was increased by danazol. However, TGFalpha mRNA expression was decreased by perphenazine. Meanwhile, mammary end-bud formation was inhibited in danazol-treated group. All findings suggest that the manifestation of the effect of TGFalpha on mammary gland is rather suppressed by PRL, while mammary gland growth needs the participation of PRL; in other words, PRL is dominant to TGFalpha on the mammary gland growth. OVX resulted in a significant decrease of TGFalpha mRNA expression in the mammary gland despite of little alteration in serum PRL, confirming the previous observations. The similar trend was observed in ICR mice; however, the response to hormonal modulation is generally less susceptible than SHN mice.

Transforming growth factor-alpha mRNA and epidermal growth factor receptor mRNA expression in normal and neoplastic mammary glands of four strains of mice with different mammary tumor potentials.

Transforming growth factor-alpha (TGF alpha) and epidermal growth factor receptor (EGF-R) mRNAs were determined by reverse transcriptase-polymerase chain reaction (RT-PCR) in the normal and neoplastic mammary glands of four strains of mice with different mammary tumor potentials (from highest to lowest potential): SHN, GR/A, SLN and C3H/He. At 2 months of age, when the mammary glands of these strains consisted mostly of normal tissue, the samples examined showed the positive expressions of both TGF alpha and EGF-R mRNAs in all strains (4-6 mice per group), except for EGF-R mRNA in the SLN mice, expressed in only 2 of 4 samples associated with no end-bud formation in the mammary glands. At 10 months, all of the samples from all four strains had a positive expression of TGF alpha mRNA. The EGF-R mRNA expression paralleled the degree of the formation of preneoplastic hyperplastic alveolar nodules (HAN) in all strains. These findings indicate that TGF alpha and EGF-R participate in the growth of the mammary glands, and that EGF-R especially contributes to the formation of end-buds at younger ages and to that of preneoplastic HAN at later ages. All of the samples of mammary tumors from four strains had positive expressions of both TGF alpha and EGF-R mRNAs.

An asymmetric slice profile: spatial alteration of flow signal response in 3D time-of-flight NMR angiography.

We introduce an asymmetric slice profile technique, which alters the spatial response of the flow signal in 3D time-of-flight NMR angiography. By gradually increasing the flip angle from the inflow to the outflow portions of the slab, the inflow refreshment effect is distributed over a wide slab thickness. The asymmetric slice profile is simply produced by using a Gaussian RF excitation with an overlapping presaturation. The spatial distribution of steady flow signal in a phantom study demonstrated an essential agreement with a numerical simulation. 3D time-of-flight NMR angiography of volunteers' heads using this technique provided a smooth vascular depiction over a wide slab thickness.

Influence of matrix size, vessel shape, vascular diameter, flow velocity, course of vessels on MR angiography.

Basic experiments were done to examine the influence of the extent of curve, direction of flow, vascular diameter, velocity of flow, and course of vessels on MR angiography. In the first experiment, two phantoms were constructed of vinyl tubing, a hairpin type and one with tubes bent to varying degrees. These phantoms were imaged in two matrices, different FOV, and of various velocities with a 1.5 Tesla system. Images of a normal volunteer were also obtained. In studies of the hairpin phantoms, a low intensity artifact appeared at the curve position, and the edge became fuzzy when the flow was perpendicular to the phase encoding direction. These phenomena were more apparent with a smaller matrix, smaller FOV, more gentle angle, larger diameter, and faster flow; in other words the component along the direction was dominant. In the phantom that used bent tubes, another low intensity artifact appeared on the medial side of the outflow portion. The results obtained from the volunteer corresponded well to those from the basic experiments. It was thought that the profile of flow was not well demonstrated due to the coarse matrix. In the second experiment, water flowed at various speeds through three-dimensional phantoms that were made of vinyl tubes of various diameters and directions. The phantoms were imaged with two- and three-dimensional time of flight and phase contrast angiography. The lower limits of detection of the phase contrast method were almost the same. In the coronal plane, the lower limit decreased to 2.5 mm for arteries and 9.5 mm for veins.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of phase-difference and complex-difference processing in phase-contrast MR angiography.

The two main phase-contrast reconstruction methods are phase difference and complex difference. The signal-to-noise ratio properties and relative advantages of the two techniques are discussed. It is argued that each processing method has applications in which it is superior, and guidelines are provided to determine those applications. It is demonstrated theoretically and experimentally that only the complex-difference method is well suited for processing phase-contrast slabs with use of a projection dephaser gradient.