University of Graz

About: University of Graz is a education organization based out in Graz, Steiermark, Austria. It is known for research contribution in the topics: Population & Quantum chromodynamics. The organization has 17934 authors who have published 37489 publications receiving 1110980 citations. The organization is also known as: Carolo Franciscea Graecensis & Karl Franzens Universität.

Association of vitamin D status with serum androgen levels in men.

Abstract: Summary Objective Studies in rodents indicate a role of vitamin D in male reproduction, but the relationship between vitamin D and androgen levels in men is largely unexplored. We aimed to investigate the association of 25-hydroxyvitamin D [25(OH)D] levels with testosterone, free androgen index (FAI) and SHBG. Moreover, we examined whether androgen levels show a similar seasonal variation to 25(OH)D. Design In this cross-sectional study, 25(OH)D, testosterone and SHBG levels were assessed by immunoassay in 2299 men who were routinely referred for coronary angiography (1997–2000). Measurements Main outcome measures were associations of 25(OH)D levels with testosterone, SHBG and FAI. FAI was calculated as testosterone (nmol/l)/SHBG (nmol/l) × 100. Results Men with sufficient 25(OH)D levels (≥30 μg/l) had significantly higher levels of testosterone and FAI and significantly lower levels of SHBG when compared to 25(OH)D insufficient (20–29·9 μg/l) and 25(OH)D-deficient (<20 μg/l) men (P < 0·05 for all). In linear regression analyses adjusted for possible confounders, we found significant associations of 25(OH)D levels with testosterone, FAI and SHBG levels (P < 0·05 for all). 25(OH)D, testosterone and FAI levels followed a similar seasonal pattern with a nadir in March (12·2 μg/l, 15·9 nmol/l and 40·8, respectively) and peak levels in August (23·4 μg/l, 18·7 nmol/l and 49·7, respectively) (P < 0·05 for all). Conclusion Androgen levels and 25(OH)D levels are associated in men and reveal a concordant seasonal variation. Randomized controlled trials are warranted to evaluate the effect of vitamin D supplementation on androgen levels.

Small-angle scattering of interacting particles. II. Generalized indirect Fourier transformation under consideration of the effective structure factor for polydisperse systems

Abstract: The indirect Fourier transformation (IFT) is the method of choice for the model-free evaluation of small-angle scattering data Unfortunately, this technique is only useful for dilute solutions because, for higher concentrations, particle interactions can no longer be neglected Thus an advanced technique was developed as a generalized version, the so-called generalized indirect Fourier transformation (GIFT) It is based on the simultaneous determination of the form factor, representing the intraparticle contributions, and the structure factor, describing the interparticle contributions The former can be determined absolutely free from model assumptions, whereas the latter has to be calculated according to an adequate model In this paper, various models for the structure factor are compared, eg the effective structure factor for polydisperse hard spheres, the averaged structure factor, the local monodisperse approximation and the decoupling approximation Furthermore, the structure factor for polydisperse rod-like particles is presented As the model-free evaluation of small-angle scattering data is an essential point of the GIFT technique, the use of a structure factor without any influence of the form amplitude is advisable, at least during the first evaluation procedure Therefore, a series of simulations are performed to check the possibility of the representation of various structure factors (such as the effective structure factor for hard spheres or the structure factor for rod-like particles) by the less exact but much simpler averaged structure factor In all the observed cases, it was possible to recover the exact form factor with a free determined parameter set for the structure factor The resulting parameters of the averaged structure factor have to be understood as apparent model parameters and therefore have only limited physical relevance Thus the GIFT represents a technique for the model independent evaluation of scattering data with a minimum of a priori information

Inhibition of nitric oxide synthesis by NG‐nitro‐L‐arginine methyl ester (L‐NAME): requirement for bioactivation to the free acid, NG‐nitro‐L‐arginine

Abstract: 1. The L-arginine derivatives NG-nitro-L-arginine (L-NOARG) and NG-nitro-L-arginine methyl ester (L-NAME) have been widely used to inhibit constitutive NO synthase (NOS) in different biological systems. This work was carried out to investigate whether L-NAME is a direct inhibitor of NOS or requires preceding hydrolytic bioactivation to L-NOARG for inhibition of the enzyme. 2. A bolus of L-NAME and L-NOARG (0.25 micromol) increased coronary perfusion pressure of rat isolated hearts to the same extent (21 +/- 0.8 mmHg; n = 5), but the effect developed more rapidly following addition of L-NOARG than L-NAME (mean half-time: 0.7 vs 4.2 min). The time-dependent onset of the inhibitory effect of L-NAME was paralleled by the appearance of L-NOARG in the coronary effluent. 3. Freshly dissolved L-NAME was a 50 fold less potent inhibitor of purified brain NOS (mean IC50 = 70 microM) than L-NOARG (IC50 = 1.4 microM), but the apparent inhibitory potency of L-NAME approached that of L-NOARG upon prolonged incubation at neutral or alkaline pH. H.p.l.c. analyses revealed that NOS inhibition by L-NAME closely correlated with hydrolysis of the drug to L-NOARG. 4. Freshly dissolved L-NAME contained 2% of L-NOARG and was hydrolyzed with a half-life of 365 +/- 11.2 min in buffer (pH 7.4), 207 +/- 1.7 min in human plasma, and 29 +/- 2.2 min in whole blood (n = 3 in each case). When L-NAME was preincubated in plasma or buffer, inhibition of NOS was proportional to formation of L-NOARG, but in blood the inhibition was much less than expected from the rates of L-NAME hydrolysis. This was explained by accumulation of L-NOARG in blood cells. 5. These results suggest that L-NAME represents a prodrug lacking NOS inhibitory activity unless it is hydrolyzed to L-NOARG. Bioactivation of L-NAME proceeds at moderate rates in physiological buffers, but is markedly accelerated in tissues such as blood or vascular endothelium.