Hydroxyl Radical-induced Strand Break Formation of Poly(U) in Anoxic Solution. Effect of Dithiothreitol and Tetranitromethane

Summary

The role of dithiothreitol (DTT) and tetranitromethane (TNM) on the yields of radiation-induced strand break formation in polyuridylic acid (poly(U)) was studied in anoxic aqueous solutions at neutral pH by low-angle laser light-scattering. From G (single-strand breaks) as a function of DTT concentration it follows that two different processes lead to OH radical-induced single-strand break (ssb) formation. Only one of the two processes, which accounts for 80 per cent of the ssb formation, is inhibited by DTT, the other one, 20 per cent, is not inhibited. The ‘repair’ process is attributed to H-donation to the C-6-yl radical of the uracil moiety. The C-6-yl radical is produced by OH addition to the C-5 position of the uracil moiety. It follows that the sugar radicals, in contrast to earlier suggestions, do not seem to be repaired by DTT at the low concentrations used. The strand break formation not inhibited by DTT is induced by radicals other than the uracil-6-yl radical, e.g. the uracil-5-yl or the OH radicals reacting with the sugar moiety. The strong reduction of G(ssb) from 2·3 to 0·2 on addition of TNM is also discussed.     

A new instrument for assessing the quality of studies on prevalence

There are numerous scientific articles of studies on the prevalence of disorders with non-standardised examination and diagnostic protocols. Because their quality is heterogeneous, a new instrument has been developed for the assessment of such studies. The new instrument is based mainly on statistical criteria. The points assigned for each of the main criteria according to the information gained from each paper are summed up to form a Total Quality Score (TQS). The interrater reliability of the instrument was tested by employing Kappa and Interrater Correlation Coefficient (ICC) statistics. The latter was assessed on the results of three independent investigators. The new quality instrument appeared to be easy to use, and the instructions were comprehensible. The ICC_(2,1) for the TQS ranged between 0.94 and 1.00 indicating almost perfect agreement between the investigators. The reliability of the new instrument enables its use for scientific review purposes. In this way, its validity will also be tested. The instrument could be adopted for assessment of scientific articles of studies on the prevalence of disorders in many, similar, scientific areas.     

Precision of jaw‐closing movements for different jaw gaps

Jaw‐closing movements are basic components of physiological motor actions precisely achieving intercuspation without significant interference. The main purpose of this study was to test the hypothesis that, despite an imperfect intercuspal position, the precision of jaw‐closing movements fluctuates within the range of physiological closing movements indispensable for meeting intercuspation without significant interference. For 35 healthy subjects, condylar and incisal point positions for fast and slow jaw‐closing, interrupted at different jaw gaps by the use of frontal occlusal plateaus, were compared with uninterrupted physiological jaw closing, with identical jaw gaps, using a telemetric system for measuring jaw position. Examiner‐guided centric relation served as a clinically relevant reference position. For jaw gaps ≤4 mm, no significant horizontal or vertical displacement differences were observed for the incisal or condylar points among physiological, fast, and slow jaw‐closing. However, the jaw positions under these three closing conditions differed significantly from guided centric relation for nearly all experimental jaw gaps. The findings provide evidence of stringent neuromuscular control of jaw‐closing movements in the vicinity of intercuspation. These results might be of clinical relevance to occlusal intervention with different objectives.     

Serum adiponectin levels in hypogonadal males: influence of testosterone replacement therapy

OBJECTIVE: Adiponectin is an adipocyte-specific secretory protein which exhibits antiatherogenic, anti-inflammatory and antidiabetic properties. We hypothesized that testosterone plays an important role in the regulation of its secretion in humans, as adiponectin concentrations are higher in women than in men and as testosterone administration is accompanied by a reduction in serum adiponectin in animals and by reduced protein secretion in cultured adipocytes. This study aimed to evaluate adiponectin levels in hypogonadal men prior to and during testosterone replacement therapy. SUBJECTS AND METHODS: In a retrospective study, adiponectin, total and free testosterone, oestradiol, SHBG, total cholesterol and triglyceride levels were evaluated in 31 hypogonadal men [HM; age, mean +/- SEM: 36.5 +/- 2.4 years; body mass index (BMI) 24.6 +/- 0.8 kg/m2] and 29 weight-matched eugonadal men (EM; age 30.8 +/- 1.5 years; BMI 23.4 +/- 0.6 kg/m2). In 13 HM (age 33.9 +/- 3.2 years; BMI 24.2 +/- 0.9 kg/m2) the same parameters were also evaluated after 6 months of testosterone replacement therapy. Correlation analysis between adiponectin and hormonal, biochemical and anthropometric parameters was performed in all subjects. RESULTS: Testosterone, free testosterone and oestradiol concentrations were significantly lower in HM than in EM (4.4 +/- 0.4 nmol/l, 78.4 +/- 10.9 pmol/l and 36.1 +/- 3.0 pmol/l, respectively, in HM vs. 21.9 +/- 0.7 nmol/l, 507.9 +/- 13.8 pmol/l and 65.2 +/- 1.8 pmol/l, respectively, in EM, P < 0.0001), while SHBG levels in HM were higher than in EM (54.4 +/- 7.5 vs. 30.9 +/- 2.2 nmol/l, P < 0.005). Serum adiponectin levels in HM were significantly higher than in EM (9.53 +/- 0.73 vs. 6.80 +/- 0.55 microg/ml, P < 0.01). Calculation of the Pearson coefficient showed that adiponectin levels in HM were not correlated with any of the anthropometric and hormonal parameters examined, but showed a significant negative correlation with serum triglycerides (r = -0.38, P < 0.05). Serum adiponectin levels were negatively correlated with body weight (r = -0.41, P < 0.05) in EM but not with other anthropometric, hormonal or biochemical parameters. Six months after initiation of testosterone replacement therapy, which increased testosterone and free testosterone levels to the normal range, adiponectin levels were significantly reduced in HM (6.37 +/- 0.93 vs. 9.26 +/- 1.01 microg/ml, P < 0.01) and similar to those recorded in EM. CONCLUSIONS: Compared to eugonadal subjects, hypogonadal men show higher adiponectin levels which are reduced by testosterone replacement therapy. This study indicates that testosterone exerts a regulatory role on adiponectin secretion in humans.