Brain aromatase in control versus castrated Norway Brown, Sprague-Dawley and Wistar adult rats.

Brain aromatase cytochrome P450 converts androgens to estrogens that play a critical role in the development of sexually dimorphic neural structures, the modulation of neuroendocrine function(s), and the regulation of sexual behavior. We characterized the influence of surgical castration on brain aromatase in Norway Brown and Wistar adult rats and compared their responses to Sprague-Dawley rats that were surgically or biochemically castrated (with flutamide, a known androgen receptor blocker). Aromata enzyme activity was measured by the tritiated water release assay in the medial basal hypothalmus/preoptic area (MBH/POA) and amygdala brain regions. The present results demonstrate that independent of the rat strain examined, MBH/POA aromatase is regulated by androgens (in Sprague-Dawley, Norway Brown and Wistar males). However, intact Wistar animals displayed significantly higher MBH/POA aromatase levels compared to Sprague-Dawley control values. Conversely, in the amygdala region, there was an apparent lack of androgen hormone action upon aromatase enzyme activity in some of the rat strains tested. The importance of brain aromatase regulating estrogen biosynthesis and influencing brain development and function is covered.

Solid-state NMR characterization of copolymers of nylon 11 and nylon 12.

Solid-state 13C and 15N NMR spectroscopy, in conjunction with differential scanning calorimetry, wide-angle X-ray diffraction and infrared spectroscopy, were used to characterize a series of nylon 11 and 12 copolymers with mole percentages of nylon 12 monomer of 0, 15, 35, 50, 65, 85, and 100%. Monotonic melting point (Tm) and heat of fusion depressions were observed for the copolymer series with the 65 mol% nylon 12 copolymer having the lowest apparent crystallinity and Tm at 148 degrees C. Solid-state 15N NMR spectra showed a smooth shift of the main peak position for the as-prepared copolymers from 84 ppm for the alpha-form of pure nylon 11 to 89 ppm for the gamma-form of pure nylon 12. Similar behavior was seen for FTIR amide V and VI modes which are also sensitive to the alpha- and gamma-crystal forms. 13C NMR T1 measurements showed that the overall most mobile sample was the 65:35 copolymer. The amide group of the 1:1 copolymer was labelled using 15N-labelled amino acids available through the Gabriel synthesis; an annealed, solution-cast film of this sample showed a T1N value of 349 s, similar to values seen for annealed nylon 11 and nylon 12 homopolymers. The WAXS pattern for the 65 mol% nylon 12 sample showed a sharp peak at 2 theta = 21.3, overlapping a broad peak centered at 2 theta = 21.0. These are consistent with the values seen for gamma-form nylon 12. The 1:1 copolymer (15N labelled) was shown to be polymorphic, like the homopolymers after specific treatments, with a gamma-like phase formed upon solvent casting, and an alpha-like phase dominating for as-polymerized material and precipitated flakes.