Dispositional resistance to change : measurement equivalence and the link to personal values across 17 nations

The concept of dispositional resistance to change has been introduced in a series of exploratory and confirmatory analyses through which the validity of the Resistance to Change (RTC) Scale has been established (S. Oreg, 2003). However, the vast majority of participants with whom the scale was validated were from the United States. The purpose of the present work was to examine the meaningfulness of the construct and the validity of the scale across nations. Measurement equivalence analyses of data from 17 countries, representing 13 languages and 4 continents, confirmed the cross-national validity of the scale. Equivalent patterns of relationships between personal values and RTC across samples extend the nomological net of the construct and provide further evidence that dispositional resistance to change holds equivalent meanings across nations.

Cortisol disrupts the ability of estradiol-17β to induce the LH surge in ovariectomized ewes

Stress disrupts the preovulatory luteinizing hormone (LH) surge in females, but the mechanisms are unknown. We tested the hypothesis that cortisol compromises the ability of estrogen to induce a preovulatory-like LH surge in ovariectomized ewes in both the breeding and nonbreeding season. Luteinizing hormone surges were induced in ovariectomized ewes by treatment with progesterone followed by a surge-inducing estradiol-17β (E2) stimulus using a crossover design. The experiment was replicated in the breeding and nonbreeding seasons. Cortisol reduced the incidence of LH surges irrespective of season. Cortisol increased the latency from E2 stimulus to the onset of the surge in the breeding season only and suppressed the LH surge amplitude during both seasons (P < 0.01). We conclude that cortisol can interfere with the LH surge in several ways: delay, blunt, and in extreme cases prevent the E2-induced LH surge. Furthermore, the effect of cortisol to delay the E2-induced LH surge is more pronounced in the breeding season. These results show that cortisol disrupts the positive feedback effect of E2 to trigger an LH surge and suggest the involvement of multiple mechanisms.

Androgen metabolism in the Australian lizard Tiliqua rugosa

Nonmammalian vertebrates possess some unusual features in their hormonal systems/ when compared to mammals. As a consequence, they can make an important contribution in investigations concerning the fundamental mechanisms operating in endocrinology. Such studies concerning androgens include inter alia their effects on developmental aspects in the brain of birds and related singing behaviour; the role of neural enzymes in reproductive processes in fish; and the relation between androgens and the stages of spermatogenesis in amphibia, The present thesis examines the biochemistry of androgens in the Australian lizard Tiliqua rugosa. The major compounds studied were testosterone and epitestosterone, which are known to be present in high concentrations in the plasma of the male animal. Previous investigations are expanded, particularly in the areas of steroid identification and testicular biosynthesis. In addition, preliminary studies on the metabolism in the brain (and other tissues) and plasma protein binding are reported. The presence of epitestosterone as a major free androgen in the plasma of the male lizard was confirmed. Other steroids were found in the sulphate fraction. Testosterone sulphate was the most rigorously identified compound, while some evidence was also found for the presence of conjugated 5-androstene-3β,17-diols, etiocholanolone and dehydroepiandrosterone (DHA). Epitestosterone does not appear to be extensively conjugated in this animal. Steroids were not found to be conjugated as glucuronides. The identification studies employed a novel method of electrochemical detection of steroids. This technique was investigated and extended in the current thesis. Biosynthetic studies were carried out on androgen interconversions in the testis, in vitro. The major enzyme activities detected were 17α-arid 17β-oxidoreductases (17α-OR and l7β-OR) and 3β-hydroxysteroid dehydrogenase (3β-HSD)/isonerase. No evidence was found for the presence of a steroid-17-epimerase that would directly interconvert testosterone and epitestosterone. The 17-oxidoreductases were found to be dependent on the cofactor NBDFH. Testosterone appears to be formed mainly via the 4-ene pathway, whereas epitestosterone is formed from both the 4- and 5-ene routes. The compound 5-androstene-3β, 17α-diol was found to be an intermediate in the synthesis of epitestosterone from DHA. Temperature was found to significantly affect 17α-OR activity (maximum at 32°C). In contrast,17β-OR activity was independent of this factor in the testis. Androgen metabolism in the testis was found to be regulated by cofactors, temperature and season. The major enzyme activities found in the male brain were 17α- and 17β-OR. 3βHSD/isomerase was not found; however a low activity of 5α-reductase was identified. Aromatase activity was not positively identified, but preliminary results suggest that it may be present at low levels. The 17-oxidoreductases were widespread throughout the brain. The 17α-OR was significantly lower in the forebrain than other brain sections. The 170-OR activity did not vary significantly throughout the organ, although there was a trend for its activity to be higher in the midbrain region (containing the hypothalamus in these sections). The concentration of endogenous steroids in brain tissue was estimated by radioimmunoassay. Epitestosterone was found throughout the organ structure, whereas testosterone was found mainly in the midbrain (containing hypothalamic regions in these sections). Correlations between enzyme activities and steroid concentrations in brain regions suggested that the main function of 17α-OR is to produce epitestosterone, whereas the 17β-OR may catalyse a more reversible reaction in vivo. Temperature was found to significantly affect both 17α- and 17β-OR activities in the brain. In contrast to the testis, the maximum activity of the brain enzymes occurred at 37°C. The level of 17α-OR activity in the male lizard (100 nmol/g tissue/h) is the highest reported for this enzyme in vertebrates. Both activities were found to be quantitatively similar in the whole brain homogenates of male and female animals, and did not vary seasonally when examined in the male. The 17-oxidoreductases were also found in most other tissues in T.rugosa, including epididymis, adrenal, kidney and liver (but not blood). This suggests that the high activities of both 17α-OR and 17β-OR are dominant features of the steroid system in this animal. The formation of 11-oxygenated compounds was found in the adrenal, in addition to the formation of polar metabolites in the kidney and liver (possibly polyhydroxylated and conjugated steroids). A preliminary investigation into the plasma binding of androgens was carried out. The insults suggest that there are several binding sites for testosterone; one with high affinity and low capacity; the other with low affinity and high capacity. Binding experiments were carried out at 32°C. At this temperature, specific binding was greater than at 25 or 37°C. From the results of competition studies it was suggested that epitestosterone (with a K(i)= 3 X 10 (-6)M for testosterone binding) regulates the binding of testosterone (K(i)=10(-7)M) and hence the concentrations of the latter steroid as a free compound in plasma. In general, the study has shown that the biochemistry of androgens in the reptile T.rugosa is largely similar to that found in other vertebrates. The major difference is a greatly increased activity of 17α-OR, which causes a higher concentration of 17α-compounds to be present in the tissues of this lizard. The physiological roles for epitestosterone are not yet clear. However it appears from this study that this steroid regulates testosterone concentrations in several tissues by either steroidogenic or binding mechanisms. Several major influences on this regulation include temperature, availability of cofactors and seasonal effects.

In vitro and immunological assessment of the estrogenic activity and concentrations of 17β-estradiol, estrone, and ethinyl estradiol in treated effluent from 45 wastewater treatment plants in Victoria, Australia

The project was conducted between May 2006 and September 2007, and involved the collection of effluent samples from 45 wastewater treatment plants (WWTPs). The 45 WWTPs included 16 lagoon-based plants and 29 with activated sludge-based processes. Permission was obtained from all the relevant water authorities to collect samples of final effluent at point of discharge to the environment, whether that was to a creek, a river, the ocean, or the land. Samples were collected on two occasions, namely, in August 2006 (winter) and late February–early March 2007 (summer), and subjected to a number of biological and chemical analyses, including toxicity tests, measurement of hormonal (estrogenic) activity using yeast-based bioassays, and measurement of specific hormonal concentrations using enzyme-linked immunosorbent assays (ELISAs). Almost all of the effluents examined showed estrogenic activity: in winter, no activity to 73 ng/l 17β-estradiol equivalents (EEQ); and in summer, no activity to 20 ng/l EEQ. On the whole, the levels of estrogenic activity observed were comparable with the range recently reported in Australia and New Zealand using human estrogen receptor-based assays (“not detected” to ~10 ng/l EEQ). The low/no bioassay response was confirmed by the chemical assessment of estradiol, estrone, and ethinyl estradiol concentrations by ELISA, which returned concentrations of these compounds for the most part below 10 ng/l.

New evidence on purchasing power parity from 17 OECD countries

There is a large literature that investigates whether or not real exchange rates are stationary in an attempt to unravel support for purchasing power parity (PPP). At best, the empirical results are mixed. This paper applies a unit root test that allows for a simultaneous structural break in the intercept and slope, shown by Sen (2003) to minimize power distortions, to examine PPP for 17 OECD countries. Our results on PPP are mixed. When the real exchange rate is based on the US dollar, evidence is found of PPP for only France, Portugal and Denmark. When the real exchange rate is based on the Deutschmark, we find evidence of PPP for Austria, Belgium, Norway, Spain, Netherlands, Switzerland, and Denmark.