Another look at regression analysis using ranked set samples with application to an osteoporosis study.

Statistical learning with ranked set samples has shown promising results in estimating various population parameters. Despite the vast literature on rank-based statistical learning methodologies, very little effort has been devoted to studying regression analysis with such samples. A pressing issue is how to incorporate the rank information of ranked set samples into the analysis. We propose two methodologies based on a weighted least squares approach and multilevel modeling to better incorporate the rank information of such samples into the estimation and prediction processes of regression-type models. Our approaches reveal significant improvements in both estimation and prediction problems over already existing methods in the literature and the corresponding ones with simple random samples. We study the robustness of our methods with respect to the misspecification of the distribution of the error terms. Also, we show that rank-based regression models can effectively predict simple random test data by assigning ranks to them a posteriori using judgment poststratification. Theoretical results are augmented with simulations and an osteoporosis study based on a real data set from the Bone Mineral Density (BMD) program of Manitoba to estimate the BMD level of patients using easy to obtain covariates.

Validity and reliability of male andropause symptoms self-assessment questionnaire among elderly males in Khuzestan province of Iran.

BACKGROUND: Andropause is a condition of decreasing testosterone in men that usually begins to occur at about 40 years of age. Many men find it difficult to acknowledge there may be a problem by refusing to even talk about the symptoms. AIMS: The study was conducted to the standards of MASSQ (2012) within male older adults to introduce a relevant criterion. MATERIALS AND METHODS: About 382 men with age range of 50-80 and with the mean age of 65.3 ± 2.32 were sampled with the cluster-ratio sampling method from the eight cities of Khuzestan province in southwestern Iran. The aged samples replied to the 25 items of MASSQ. RESULTS: Coefficients of Cronbach's alpha (α = 0.89), split-half (0.91), convergent validity (0.72), divergent validity (-0.32), and criterion validity (0.67) were estimated, which were significant at P < 0.01. The exploratory factor analysis demonstrated that the 25-items of MASSQ for aged samples are organized into four factors (sexual, somatic, psychic, and behavioral) which clarify 79% of the scale's variance. Second-order confirmatory factor analysis pointed out that the factors are well-matched up onto a principal factor. Consequently, the four-factor model was well appropriate for the data by the fit index techniques for adjusting the scale [adjusted goodness of fit index = 0.92, goodness-of-fit statistic = 0.91, root mean square error of approximation = 0.006, incremental fit index = 0.94, normed fit index = 0.91, comparative fit index = 0.97]. CONCLUSIONS: The results pointed to the well-adjusted reliability and validity of MASSQ and its usefulness for the relevant studies as well.

Ascorbic acid antagonizes nicotine-induced place preference and behavioral sensitization in mice.

In the present study, the influence of ascorbic acid on the nicotine-induced behavioral sensitization and conditioned place preference was investigated in mice. In the place preference paradigm, intraperitoneal (i.p.) nicotine (1 and 1.5 mg/kg, three drug sessions) but not ascorbic acid (1, 10, 100 and 1000 mg/kg) administration induced place preference. Ascorbic acid administration (10, 100 and 1000 mg/kg, i.p.) reduced both the acquisition and expression of nicotine-induced place conditioning. Locomotor sensitization in mice was produced by intraperitoneal injection of nicotine (0.25 mg/kg) for 7 consecutive days. On the 9th day of the experiments, activity of the mice was recorded after challenge with nicotine (0.1 mg/kg, i.p.). Ascorbic acid (10, 100 and 1000 mg/kg, i.p.) was injected 20 min before each injection of nicotine (acquisition of sensitization) or acutely 20 min before a challenge nicotine injection (expression of sensitization). It was shown that ascorbic acid attenuated the acquisition of nicotine sensitization in a dose-independent manner but the expression of nicotine-induced sensitization was not affected by ascorbic acid. In conclusion, it seems that ascorbic acid may interfere with nicotine-induced place preference and behavioral sensitization in mice.

Cross-tolerance between morphine- and nicotine-induced conditioned place preference in mice.

The acquisition of morphine and nicotine conditioned place preference (CPP) and cross-tolerance between the response of two drugs was studied in mice. A biased CPP paradigm was used to study the effect of the agents. Morphine (5 mg/kg) and nicotine (1 mg/kg) induced CPP. Naloxone (0.5, 1 and 2 mg/kg), but not mecamylamine (0.025, 0.05 and 0.1 mg/kg), induced conditioned place aversion (CPA). Both antagonists reversed CPP induced by morphine and nicotine. Administration of one daily dose of morphine (12.5, 25 or 50 mg/kg) for 3 days or nicotine (0.5, 1 or 2 mg/kg) three times a day for 12 days, in order to develop tolerance to the drugs, reduced the conditioning induced by morphine (5 mg/kg) or nicotine (1 mg/kg). CPA-induced by naloxone was reduced in animals, which were rendered tolerant to morphine (50 mg/kg) or nicotine (2 mg/kg). Mecamylamine, however, which did not induce any response in the nontolerant mice, elicited CPP in the tolerant animals. It is concluded that there may be a cross-tolerance between morphine- and nicotine-induced CPP.