Dual phased array coils for high-resolution MRI of the shoulder.

We connected two 3-inch coils to a dual phased array receiver system and sandwiched the shoulder between the two coils. To obtain a quantitative assessment of the improved SNR, we imaged a phantom with both the dual phased array coils and the standard shoulder coil. SNR as a function of distance from the coils was computed by the National Electrical Manufacturers Association (NEMA) standard. At the expected depth of the humeral head, the SNR of the phased array coils on single excitation was 1.42 times that of the standard shoulder coil on two excitations. The higher quality of the images on single excitation shortened the imaging procedure. The dual phased array coils realized the minimum FOV: 8 cm with a pixel of 0.31 x 0.41 mm. The dual phased array coils achieved high spatial resolution images of the shoulder with significantly shorter imaging times.

Phosphorylated and dephosphorylated types of non-activated glucocorticoid receptor.

We purified glucocorticoid receptors quickly but very partially using DEAE-resin. [3H]-Triamcinolone acetonide-labeled and non-activated receptors in the quickly purified fraction were found to be separated into two fractions (P-2 and P-3) by hydroxyapatite column chromatography. The P-2 receptor was the main component, and the ratio of P-2/P-3 was around 2. The molecular weights of the two receptors were calculated to be the same, 242,000: Rs = 6.2 nm and s20,w = 9.0. Treatment of the receptor with catalytic subunits of phosphoprotein phosphatase 2A1 reduced the P-2/P-3 ratio from 2 to 0.5, while treatment with catalytic subunits of cAMP-dependent protein kinase and ATP increased it to 2.5. The isolated P-3 receptor could be converted into the P-2 type by the kinase treatment. Tungstate, a phosphatase inhibitor, stabilized the P-2 receptor, and the P-2/P-3 ratio was larger than 3 when the DEAE-fraction was prepared in the presence of tungstate. However, the tungstate effect was not very strong, and the P-2 type tended to change into the P-3. [3H]-Triamcinolone acetonide-labeled and non-activated receptors were purified very highly by using an affinity gel; the procedure required more than 10 h. Only the P-3 form was observed in the preparation of highly purified receptors. Hormone-free receptors were affected by neither the phosphatase nor the kinase. The results indicate that the hormone binding makes the receptor sensitive to phosphatase. The reversibly dephosphorylated receptor is more stable than the non-dephosphorylated one, and can be activated.

Identical properties of aldosterone and corticosterone binders and their presence in rat brain and kidney.

The [3H]corticosterone binders from rat brain and kidney were characterized by binding affinity and chromatographies, and compared with the binders for [3H]aldosterone and [3H]triamicinolone acetonide. Corticosterone-binding globulin-like molecules at very high concentrations in crude extracts were completely eliminated by a DEAE-gel adsorption procedure. [3H]Aldosterone binder in the renal, DEAE-treated fraction was recovered in a single peak by gel-filtration chromatography and by ultracentrifugation in linear sucrose gradients, independent of hormone-binding and tungstate, a stabilizer of the binder. The Stokes' radius and sedimentation coefficient of the renal aldosterone binder were 6.6 nm and 9.3S, respectively, indicating an apparent molecular weight of 263,000. Corticosterone-preferring binder also existed in the DEAE-treated fraction. Both aldosterone and corticosterone binders were found in the brain and kidney preparations. Comparison among the binders showed identical values of Stokes' radius and elution pattern from DEAE-Toyopearl in a linear salt gradient regardless of the organ and the hormones. Scatchard analyses of [3H]aldosterone and [3H]corticosterone binding showed for each ligand only one group of high-affinity sites with the equivalent dissociation constants, 4-7 nM. The orders of steroids in competing for the two high-affinity sites were equivalent: corticosterone greater than or equal to aldosterone much greater than triamcinolone acetonide, and that for the triamcinolone acetonide binding was triamcinolone acetonide much greater than aldosterone greater than or equal to corticosterone. Hydroxyapatite column chromatography separated the aldosterone and corticosterone binders from the triamcinolone acetonide binder, but not the aldosterone binder from the corticosterone binder. It is concluded that aldosterone and corticosterone binders distinct from triamcinolone acetonide binder exist in rat brain and kidney.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of selenite on glucocorticoid receptor.

Rat liver glucocorticoid receptor was partially purified and characterized for its hormone binding using selenite. Selenite at very low concentrations irreversibly inhibited the hormone binding. The concentration for half maximal inhibition was approximately 2.8 microM. The inhibition was restored by dithiothreitol. The receptor-hormone complex became considerably insensitive to the selenite inhibition. The receptor inhibited by selenite was eluted at the same position as the native receptor from DEAE ion exchange and gel filtration columns. The results suggest that at least four sulfhydryl groups are located in the hormone binding domain of the receptor making a cluster.

Effect of dobutamine on adenylate cyclase activity in rabbit renal pelvis and ureter.

The adenylate cyclase activity in the rabbit renal pelvis and ureter was measured by the method of Salomon et al. (1974). The dobutamine-induced increase of adenylate cyclase activity is more prominent in the renal pelvis including the pacemaker region than in the ureter that is non-pacemaker region in the upper urinary tract. Therefore, it is thought that the pacemaker region is different from other regions in the upper urinary tract with regard to responses to dobutamine.

Sulfhydryl groups of aldosterone receptors from swine kidney.

Specific [3H]aldosterone binding activity in swine kidney cytosol was inactivated by pretreatment of the cytosol with monoiodoacetamide (pH 8.5), N-ethylmaleimide (pH 7.0), or 5,5'-dithiobis(2-nitrobenzoate) (pH 7.5). Dithiothreitol restored the specific binding activity inactivated by the nitrobenzoate, but not that inactivated with ethylmaleimide. Incubation of the cytosol with aldosterone prior to pretreatment with ethylmaleimide protected the receptors from inactivation. The rank order of steroids for the protection was: aldosterone greater than hydrocortisone greater than or equal to dexamethazone = progesterone greater than triamcinolone greater than estradiol. The initial velocity of the specific hormone binding could be determined by the binding reaction for 60 sec at 30 degrees. Double reciprocal plots of the initial velocity versus the hormone concentration with or without the nitrobenzoate showed a typical pattern of competition between the hormone and the inactivator. The results indicated the presence of functional sulfhydryl groups on the hormone binding sites of aldosterone receptors.