Delay discounting and probability discounting as related to cigarette smoking status in adults

This study examined relations between adult smokers and non-smokers and the devaluation of monetary rewards as a function of delay (delay discounting, DD) or probability (probability discounting, PD). The extent to which individuals discount value, either as a function of a reward being delayed or probabilistic, has been taken to reflect individual differences in impulsivity. Those who discount most are considered most impulsive. Previous research has shown that adult smokers discount the value of delayed rewards more than adult non-smokers. However, in the one published study that examined probability discounting in adult smokers and non-smokers, the smokers did not discount the value of probabilistic rewards more than the non-smoker controls. From this past research, it was hypothesized that measures of delay discounting would differentiate between smokers and non-smokers but that probability discounting would not. Participants were 54 (25 female) adult smokers (n = 25) and non-smokers (n = 29). The smokers all reported smoking at least 20 cigarettes per day, and the non-smokers reported having never smoked. The results indicated that the smokers discounted significantly more than the non-smokers by both delay and probability. Unlike past findings, these results suggest that both delay and probability discounting are related to adult cigarette smoking; however, it also was determined that DD was a significantly stronger predictor of smoking than PD.     

Delay discounting and gambling

Delay discounting describes the decline in the value of a reinforcer as the delay to that reinforcer increases. A review of the available studies revealed that steep delay discounting is positively correlated with problem or pathological gambling. One hypothesis regarding this correlation derives from the discounting equation proposed by Mazur (1989). According to the equation, steeper discounting renders the difference between fixed-delayed rewards and gambling-like variable-delayed rewards larger; with the latter being more valuable. The present study was designed to test this prediction by first assessing rats’ impulsive choices across four delays to a larger-later reinforcer. A second condition quantified strength of preference for mixed- over fixed-delays, with the duration of the latter adjusted between sessions to achieve indifference. Strength of preference for the mixed-delay alternative is given by the fixed delay at indifference (lower fixed-delay values reflect stronger preferences). Percent impulsive choice was not correlated with the value of the fixed delay at indifference and, therefore, the prediction of the hyperbolic model of gambling was not supported. A follow-up assessment revealed a significant decrease in impulsive choice after the second condition. This shift in impulsive choice could underlie the failure to observe the predicted correlation between impulsive choice and degree of preference for mixed- over fixed delays.     

Percent body fat is related to delay and probability discounting for food in humans

This study describes delay and probability discounting patterns for hypothetical food and money in relation to percent body fat (PBF). Sixty university students completed four computerized discounting tasks in which they were asked to make a series of hypothetical decisions between (a) 10 dollars after one of several different delays (1, 2, 30, 180, and 365 days) or a smaller amount of money available immediately; (b) 10 bites of food after one of several delays (1, 2, 5, 10, and 20 h) or a smaller number of bites available immediately; (c) $10 at one of several probabilities (0.9, 0.75, 0.5, 0.25, 0.1) or a smaller amount of money to be received for sure; and (d) 10 bites of food at one of several probabilities (0.9, 0.75, 0.5, 0.25, 0.1) or a smaller number of bites to be received for sure. Median indifference points for all participants across each task were well described using the hyperbolic discounting function. Results suggest that percent body fat predicted discounting for hypothetical food, but not money, using regression analyses with the entire sample and when comparing individuals in the high and low quartiles for PBF. None of the other dietary variables (body mass index, subjective hunger, and time since last meal or snack) were related to discounting patterns. This suggests that individuals with high PBF may exhibit heightened sensitivities to delay and probability when making decisions about food.     

Using crowdsourcing to examine relations between delay and probability discounting

Although the extensive lines of research on delay and/or probability discounting have greatly expanded our understanding of human decision-making processes, the relation between these two phenomena remains unclear. For example, some studies have reported robust associations between delay and probability discounting, whereas others have failed to demonstrate a consistent relation between the two. The current study sought to clarify this relation by examining the relation between delay and probability discounting in a large sample of internet users (n = 904) using the Amazon Mechanical Turk (AMT) crowdsourcing service. Because AMT is a novel data collection platform, the findings were validated through the replication of a number of previously established relations (e.g., relations between delay discounting and cigarette smoking status). A small but highly significant positive correlation between delay and probability discounting rates was obtained, and principal component analysis suggested that two (rather than one) components were preferable to account for the variance in both delay and probability discounting. Taken together, these findings suggest that delay and probability discounting may be related, but are not manifestations of a single construct (e.g., impulsivity).     

Delay discounting of saccharin in rhesus monkeys

The value of a reinforcer decreases as the time until its receipt increases, a phenomenon referred to as delay discounting. Although delay discounting of non-drug reinforcers has been studied extensively in a number of species, our knowledge of discounting in non-human primates is limited. In the present study, rhesus monkeys were allowed to choose in discrete trials between 0.05% saccharin delivered in different amounts and with different delays. Indifference points were calculated and discounting functions were established. Discounting functions for saccharin were well described by a hyperbolic function. Moreover, the discounting rates for saccharin in all six monkeys were comparable to those of other non-human animals responding for non-drug reinforcers. Also consistent with other studies of non-human animals, changing the amount of a saccharin reinforcer available after a 10-s delay did not affect its relative subjective value. Discounting functions for saccharin were steeper than we found in a previous study with cocaine, raising the possibility that drugs such as cocaine may be discounted less steeply than non-drug reinforcers.     

Plasmodesmal changes are related to different developmental stages of antheridia of Chara species

Summary During the development of the antheridia of Chara species, dynamic changes in the occurrence and ultrastructure of plasmodesmata are observed which are closely correlated to particular developmental phases and presumably regulate the morphogenetic events in the antheridia. The disappearance of plasmodesmata between shield cells and between shied cells and the basal cell leads to a cessation in symplasmic transport around the antheridum and determines its concentric or centrifugal character via centrally situated capitular cells. Unplugged plasmodesmata are present between fully synchronously developing antheridial filament cells and obviously coordinate the development of the cells. In the middle phase of spermiogenesis, rough endoplasmic reticulum in antheridial filaments passes uncompressed through wide plasmodesmata and provides an additional transport pathway for developmental control factors. Plugged plasmodesmata link cells of different types or cells of the same type which are at different phases of cell cycle and guarantee their individual development. The plugging of plasmodesmata is a reversible process that depends on the morphogenetic situation. Plasmodesmata connecting the basal cell and the subbasal cell as well as the basal cell and capitular cells are transformed successively from the simple into the complex type and might be the pathways for an import of gibberellins and nutrients into the strong sink tissues of the developing antheridium. There is a symplasmic connection between the antheridum and the thallus via a basal cell. Prior to the initiation of spermatozoid differentiation (spermiogenesis), plasmodesmata connecting the basal cell with a subbasal cell and the basal cell with capitular cells are spontaneously broken, resulting in symplasmic isolation of the antheridium that is probably a signal which triggers the induction of spermatozoid differentiation. Premature plasmolytically evoked symplasmic isolation of the antheridium leads to the elimination of 1 to 2 cell cycles from the proliferative stage of spermatogenesis. Autoradiographic studies demonstrate that both natural and induced symplasmic isolation drastically decreases the entry of isotopically labeled gibberellic acid into antheridia of Chara species that may be the consequence of the elimination of the hormone's transport through plasmodesmata.Correspondence and reprints: Department of Cytophysiology, University of ód, ulica Pilarskiego 14, 90-231 ód, Poland.Received March 11, 2002; accepted September 19, 2002; published online August 26, 2003     

Some antioxidant and senescence parameters of broccoli as related to its developmental stages

In broccoli heads grown in spring and in autumn, and harvested at four various developmental stages antioxidant ability as well as certain indices of plant senescence were investigated. Development of broccoli heads was accompanied by losses of chlorophyll and ascorbic acid. At pre-florescence stage accumulation of soluble phenolics was observed. Activity of peroxidase in the initial stage of growth increased significantly and its high level was mantained during the whole growing period. The profound evolution of ethylene was manifested by plants of the pre-florescence stage. In broccoli grown in spring the higher contents of chlorophyll and phenolics in comparison with the autumn experiment were observed, as well as slightly higher activities of peroxidase and catalase. Total antioxidant activity was considerably higher in spring than in autumn.     

Comparative study of maximal midexpiratory flow rate in normal smoking and non-smoking subjects

MMF is considered one of the most sensitive parameter to point out initial decay of small airways that should appear prematurely in smokers as compared with non smokers. To verify the above we tested male subjects apparently free from any respiratory disease. They were classed into two groups of equal number: the first group of smokers, the second one of non smokers. We did not find any statistically significant difference between the two groups: this is probably due to the young age of the subjects and consequently to the relative short period of exposure to tobacco smoke.     

On the scaling interpretation of exponents in hyperboloid models of delay and probability discounting

Previously, we (McKerchar et al., 2009) showed that two-parameter hyperboloid models ( [Green and Myerson, 2004] and [Rachlin, 2006]) provide significantly better fits to delay discounting data than simple, one-parameter hyperbolic and exponential models. Here, we extend this effort by comparing fits of the two-parameter hyperboloid models to data from a larger sample of participants (N = 171) who discounted probabilistic as well as delayed rewards. In particular, we examined the effects of amount on the exponents in the two hyperboloid models of delay and probability discounting in order to evaluate key theoretical predictions of the standard psychophysical scaling interpretation of these exponents. Both the Rachlin model and the Green and Myerson model provided very good fits to delay and probability discounting of both small and large amounts at both the group and individual levels (all R²s > .97 at the group level; all median R²s > .92 at the individual level). For delay discounting, the exponent in both models did not vary as a function of delayed amount, consistent with the psychophysical scaling interpretation. For probability discounting, however, the exponent in both models increased as the probabilistic amount increased—a finding inconsistent with the scaling interpretation.     

Children's coughs related to parental smoking.

A survey of the smoking habits, attitudes, and background of over 15 000 8-19 year olds in northern England in December 1982 showed a positive correlation between parental smoking and the reporting of frequent coughs by children who had never smoked. This was especially pronounced in the youngest children. Thirty five per cent of boys under 11 who had never smoked and whose parents did not smoke reported frequent coughs; with one parent smoking this increased to 42%, and when both parents smoked the proportion was 48%. Girls under 11 showed the same pattern, with 32%, 40%, and 52% respectively reporting frequent coughs. Fewer older children in general reported frequent coughs. Mothers'' smoking had more influence on children''s coughs than had fathers'' smoking. Social area type had no significant effect. No significant effect of passive smoking was observed when the children themselves were smokers. These results are clear evidence of a definite link between smoking in the home and coughs in young children, which not only may present immediate problems but may also be a cause of illness in the future.     

Characterization of the heat shock protein 90 gene in the plant parasitic nematode Meloidogyne artiellia and its expression as related to different developmental stages and temperature

The full-length cDNA and the corresponding gene of the heat shock protein 90, Mt-Hsp90, were isolated and characterized in the plant parasitic nematode Meloidogyne artiellia. The full-length Mt-Hsp90 cDNA contained a 5′ untranslated region (UTR) of 45 bp with the 22 bp trans-spliced leader SL1, an ORF of 2172 bp encoding a polypeptide of 723 amino acids and a 3′ UTR of 191 bp. The deduced amino acid sequence of Mt-hsp90 showed high similarity with other known Hsp90s. Five conserved amino acid signatures indicated that Mt-hsp90 is a cytosolic member of the Hsp90 family. The gene consists of 10 exons and 9 introns, a more expanded gene structure compared to the corresponding Caenorhabditis elegans gene, daf-21. Mt-hsp90 gene was constitutively expressed at high levels in all developmental stages of M. artiellia. Egg masses and second stage juveniles (J2s) were exposed at 5° and 30 °C for different periods of times in order to explore the impact of adverse temperature on Mt-hsp90 gene expression. Expression levels of Mt-hsp90 were examined by fluorescent real-time PCR. At 30 °C a burst of expression for Mt-hsp90 was observed in J2s after 2 h of heat shock treatment, then expression dropped with longer exposing times, although remaining still relatively high after 24 h. This temperature did not affect Mt-hsp90 gene expression in the egg masses. However, egg masses exposed at 5 °C showed a little but gradual increase in the mRNA level with time. By contrast, no significant changes in the Mt-hsp90 level were observed in J2s exposed to cold. These data show that egg masses and J2s exposed to cold and heat stresses have different expression profiles suggesting that Mt-Hsp90 may provide a link between environmental conditions and the life cycle of the nematode.     

Absence from school related to children's and parental smoking habits.

A sample of 2885 children aged 12 and 13 who completed a questionnaire survey in school in January 1987 were given a second questionnaire on a specified date in May 1987. The smoking habits, parental smoking habits, sex, and social background of the children who were present on both dates were compared with those of the children who were absent on the second occasion. Regular smoking was significantly more common among those absent for the second questionnaire: among boys 181/877 (21%) who never smoked, 109/486 (22%) who sometimes smoked, and 21/45 (47%) who regularly smoked were absent, and among girls the figures were 157/947 (17%), 117/487 (24%), and 17/43 (40%) respectively. Thus the odds ratio for those who sometimes smoked was 1.29 and for regular smokers 3.09 against those who never smoked. Whatever the children''s smoking habits, the proportion who were absent was higher when both parents or at least the mother smoked, the odds ratio being 1.39; the proportions absent were 203/1180 (17%) if neither parent or only the father smoked v 135/644 (21%) if both parents or only mother smoked for children who never smoked; 105/529 (20%) v 121/444 (27%) for those who sometimes smoked; and 10/27 (37%) v 28/61 (46%) for those who regularly smoked. Sex and social background had little effect, though there was an overall higher rate of absence among boys from industrial areas. The findings show a higher rate of minor ailments in children who smoke and in children whose mother smokes. If children are having frequent days off school for minor ailments possibly they or their parents would benefit from advice and help in stopping smoking.     

Damage to DNA in cervical epithelium related to smoking tobacco.

OBJECTIVE--To determine whether tobacco smoking causes increased DNA modification (adducts) in human cervical epithelium. DESIGN--Comparison of DNA adducts measured by the technique of postlabelling with phosphorus-32 in normal ectocervical epithelium of smokers and non-smokers. A questionnaire on smoking habit and a urinary cotinine assay were used to identify smokers and non-smokers. SETTING--Cytology unit in large teaching hospital. SUBJECTS--39 women (11 current smokers, seven former smokers, and 21 who had never smoked) undergoing gynaecological treatment (colposcopy or hysterectomy). Nineteen members of staff who did not smoke as controls. INTERVENTIONS--Biopsy of normal ectocervical epithelium. Urine sample. MAIN OUTCOME MEASURES--Measurement of DNA adducts in cervical epithelial tissue of smokers and non-smokers. Smoking habit derived from results of questionnaire and urinary cotinine:creatinine ratio. Proportion of adducts in women with abnormal and normal results of cervical smear test. RESULTS--DNA samples from smokers (identified from questionnaire) had significantly higher median proportions of DNA adducts that non-smokers (4.62 (95% confidence interval 4.04 to 7.74) v 3.47 (2.84 to 4.78) adducts/10(8) nucleotides; p = 0.048). Exclusion of women whose urinary cotinine:creatinine ratio did not confirm their self reported smoking habit (smoker or non-smoker) increased this difference (4.7 (3.85 to 8.08) v 3.52 (2.32 to 4.95) adducts/10(8) nucleotides; p = 0.03). Women who had abnormal results of cervical smear tests had significantly higher proportions of adducts than those with normal results (4.7 (3.90 to 8.13) v 3.47 (3.06 to 5.36) adducts/10(8) nucleotides; p = 0.03). CONCLUSIONS--Tobacco smoking by women leads to increased modification of DNA in cervical epithelium, suggesting biochemical evidence consistent with smoking as a cause of cervical cancer.     

Testosterone related to age and life-history stages in male baboons and geladas

Despite significant advances in our knowledge of how testosterone mediates life-history trade-offs, this research has primarily focused on seasonal taxa. We know comparatively little about the relationship between testosterone and life-history stages for non-seasonally breeding species. Here we examine testosterone profiles across the life span of males from three non-seasonally breeding primates: yellow baboons (Papio cynocephalus or P. hamadryas cynocephalus), chacma baboons (Papio ursinus or P. h. ursinus), and geladas (Theropithecus gelada). First, we predict that testosterone profiles will track the reproductive profiles of each taxon across their respective breeding years. Second, we evaluate age-related changes in testosterone to determine whether several life-history transitions are associated with these changes. Subjects include males (> 2.5 years) from wild populations of each taxon from whom we had fecal samples for hormone determination. Although testosterone profiles across taxa were broadly similar, considerable variability was found in the timing of two major changes: (1) the attainment of adult levels of testosterone and (2) the decline in testosterone after the period of maximum production. Attainment of adult testosterone levels was delayed by 1 year in chacmas compared with yellows and geladas. With respect to the decline in testosterone, geladas and chacmas exhibited a significant drop after 3 years of maximum production, while yellows declined so gradually that no significant annual drop was ever detected. For both yellows and chacmas, increases in testosterone production preceded elevations in social dominance rank. We discuss these differences in the context of ecological and behavioral differences exhibited by these taxa.     

Activity of glutathione related enzymes and ovarian steroid hormones in different sizes of follicles from goat and sheep ovary of different reproductive stages

The investigations on enzymes related to glutathione like glutathione-S-transferase (GST) and glutathione peroxidase (GSH-Px) have been carried out mostly in human and rat ovaries, however the studies on these enzymes in ruminants are relatively absent. In the present study the changes in the activity of these enzymes, in different sizes of follicles from goat and sheep ovaries of different reproductive stages, were investigated. The results demonstrated that the activity of the enzyme GST increased with the increase in size of the follicles from small to large follicles of follicular phase ovary and from small to medium follicles of luteal phase ovary in both the species, thereafter it decreased in large follicles of luteal phase ovary. There was increasing pattern in the activity of GSH-Px in the follicular phase follicles and a decreasing pattern in the luteal phase follicles from both the species. Thus the changes in the activity of glutathione related enzymes namely GST and GSH-Px in different size follicles from both the species during different reproductive phases are evident from the results. It is reasonable, therefore, to assume that these enzymes may have functional role in the steroid hormone metabolism in ruminant ovary as reported in human ovary.