Impulsivity, aggression, and suicidality relationship in adults: A systematic review and meta-analysis

BACKGROUND

The aim of the study was to crystallize the nature of relationships between impulsivity, aggression, and suicidality. We reviewed studies of adults with published, psychometric measures of impulsivity and aggression, and measures of suicidality.

METHODS

Our primary data source was Web of Science (from inception to 31st December 2021). Quality of articles was assessed using a Joanna Briggs Appraisal Tool and publication bias using Trim and Fill. We synthesised results using random effects meta-analyses and explored moderation by measure of impulsivity, aggression, and suicidality, and population.

FINDINGS

77 studies were included in our analysis. We found weak positive relationships between impulsivity (r = 0·19 [95% CI: 0·15-0·22]), aggression (0·23 ([0·17, 0·29]), and impulsive aggression (0·16 [0·1, 0·22]) with suicidality. Heterogeneity was significant and only partially explained by moderators. Limitations included the lack of studies which assess impulsivity or aggression proximal to suicidality.

INTERPRETATION

Given small effect sizes and significant heterogeneity, the study suggests that additional studies are needed in the field to analyze the relation between impulsivity and aggression with suicidality.

FUNDING

None.

Sociodemographic predictors of attendance at a Scottish pain management programme

We examined relationships between various sociodemographic factors and attendance at the Glasgow Pain Management Programme (n = 2899 from 2011 to 2019). We tested for associations between gender, age and socioeconomic deprivation of patients who were invited to attend, and uptake to a programme when invited, attendance at screening assessment, eligibility, adherence and attendance at 3- and 6-month reviews. Uptake was significantly higher for patients from more affluent areas (95% confidence interval (CI) = 0.93–0.99, p = 0.002) and for older patients (95% CI = 0.98–0.99, p = 0.006), although effect sizes were very small. Patients were significantly more likely to be assessed as suitable if they were younger (95% CI = 0.98–0.99, p = 0.013) or female (95% CI = 0.55–0.84, p < 0.001). Attendance at sessions and at 3- and 6-month reviews was higher for patients from more affluent areas (95% CI = 1–1.09, p = 0.001, and 95% CI = 1–1.1, p = 0.044 respectively). We argue that there are multiple potential explanations for these findings and that future work should attempt to determine whether these patterns replicate in other populations and to determine any modifiable causes.

Association between psychotropic drug prescription and suicide rates in Scotland: population study

Aims and method

Rates of prescriptions of antidepressants and suicide are inversely correlated at an epidemiological level. Less attention has been paid to relationships between other drugs used in mental health and suicide rates. Here we tested relationships between prescriptions of anxiolytics and antipsychotics and suicide rates in Scotland.

Results

Suicide rates were inversely correlated with prescriptions of antidepressants and antipsychotics over 14 years (2004–2018), and positively with prescriptions of anxiolytics.

Clinical implications

This illustrates the role of medications used in mental health in suicide prevention, and highlights the importance of identifying causal mechanisms that link anxiolytics with suicide.

Socioeconomic position, immune function, and its physiological markers

The development of costly traits such as immune function and secondary sexual traits is constrained by resource availability. The quality of developmental conditions and the availability of resources in ontogeny may therefore influence immune system functions and other biological traits. We analyzed causal pathways between family socioeconomic position, strength of immune response, and five physiological biomarkers in young Latvian men (n = 93) using structural equation modeling. Men from wealthier families had higher testosterone levels (r_s = 0.280), stronger immune response (r_s = 0.551), and higher facial attractiveness (r_s = 0.300). There were weak, non-significant correlations between family income, body fat percentage (r_s = -0.147), and fluctuating asymmetry (r_s = -0.159). Testosterone partially (33.8%) mediated the effect of family income on facial masculinity. Testosterone (positively) and adiposity (negatively) partially (4%) mediated the relationship between family income and immune function. Higher facial masculinity, higher facial symmetry, and lower adiposity were reliable and independent cues of better immune function (R² = 0.238) in a larger sample of young Latvian men (N = 146). Resource availability in ontogeny has an important role for the development of immune function and physical appearance, and it is a key parameter to be included in human eco-immunological research.

Women's socioeconomic position in ontogeny is associated with improved immune function and lower stress, but not with height

Immune function, height and resource accumulation comprise important life history traits in humans. Resource availability models arising from life history theory suggest that socioeconomic conditions influence immune function, growth and health status. In this study, we tested whether there are associations between family income during ontogeny, adult height, cortisol level and immune response in women. A hepatitis B vaccine was administered to 66 young Latvian women from different socioeconomic backgrounds, and blood samples were then collected to measure the level of antibodies that the women produced in response to the vaccination. Cortisol levels were measured from plasma samples pre- and post-vaccination. Women from wealthier families had lower cortisol levels, and women from the highest family income group had the highest levels of antibody titers against hepatitis B vaccine. No significant relationships were observed between cortisol level and immune function, nor between family income and height. The results show that income level during ontogeny is associated with the strength of immune response and with psychoneuroendocrine pathways underlying stress perception in early adulthood. The findings indicate that the quality of the developmental niche is associated with the condition-dependent expression of immune function and stress response.

Effects of the Sex Ratio and Socioeconomic Deprivation on Male Mortality

We explored relationships between male mortality and the sex ratio. (We tested relationships across 142 societies and in longitudinal data from Scotland. A male-biased sex ratio was associated with reduced mortality by intentional self-harm across 142 societies. This was replicated in longitudinal Scottish data, and men were less likely to die by suicide and assault when there were more men in the population only when levels of unemployment were low. We argue that this is consistent with a theoretical model in which men increase investment in relationships and offspring as "competition" under a male-biased sex ratio, and that the conflicting results of previous work may stem from divergent effects of the sex ratio on mortality depending upon relative deprivation.

Women's self-rated attraction to male faces does not correspond with physiological arousal

There has been little work to determine whether attractiveness ratings of faces correspond to sexual or more general attraction. We tested whether a measure of women’s physiological arousal (pupil diameter change) was correlated with ratings of men’s facial attractiveness. In Study 1, women rated the faces of men for whom we also measured salivary testosterone. They rated each face for attractiveness, and for desirability for friendship and long- and short-term romantic relationships. Pupil diameter change was not related to subjective ratings of attractiveness, but was positively correlated with the men’s testosterone. In Study 2 we compared women’s pupil diameter change in response to the faces of men with high versus low testosterone, as well as in response to non-facial images pre-rated as either sexually arousing or threatening. Pupil dilation was not affected by testosterone, and increased relatively more in response to sexually arousing than threatening images. We conclude that self-rated preferences may not provide a straightforward and direct assessment of sexual attraction. We argue that future work should identify the constructs that are tapped via attractiveness ratings of faces, and support the development of methodology which assesses objective sexual attraction.

Effects of food quality on trade-offs among growth, immunity and survival in the greater wax moth Galleria mellonella

The resources available to an individual in any given environment are finite, and variation in life history traits reflect differential allocation of these resources to competing life functions. Nutritional quality of food is of particular importance in these life history decisions. In this study, we tested trade-offs among growth, immunity and survival in 3 groups of greater wax moth (Galleria mellonella) larvae fed on diets of high and average nutritional quality. We found rapid growth and weak immunity (as measured by encapsulation response) in the larvae of the high-energy food group. It took longer to develop on food of average nutritional quality. However, encapsulation response was stronger in this group. The larvae grew longer in the low-energy food group, and had the strongest encapsulation response. We observed the highest survival rates in larvae of the low-energy food group, while the highest mortality rates were observed in the high-energy food group. A significant negative correlation between body mass and the strength of encapsulation response was found only in the high-energy food group revealing significant competition between growth and immunity only at the highest rates of growth. The results of this study help to establish relationships between types of food, its nutritional value and life history traits of G. mellonella larvae.

A face for all seasons: Searching for context-specific leadership traits and discovering a general preference for perceived health

Previous research indicates that followers tend to contingently match particular leader qualities to evolutionarily consistent situations requiring collective action (i.e., context-specific cognitive leadership prototypes) and information processing undergoes categorization which ranks certain qualities as first-order context-general and others as second-order context-specific. To further investigate this contingent categorization phenomenon we examined the "attractiveness halo"-a first-order facial cue which significantly biases leadership preferences. While controlling for facial attractiveness, we independently manipulated the underlying facial cues of health and intelligence and then primed participants with four distinct organizational dynamics requiring leadership (i.e., competition vs. cooperation between groups and exploratory change vs. stable exploitation). It was expected that the differing requirements of the four dynamics would contingently select for relatively healthier- or intelligent-looking leaders. We found perceived facial intelligence to be a second-order context-specific trait-for instance, in times requiring a leader to address between-group cooperation-whereas perceived health is significantly preferred across all contexts (i.e., a first-order trait). The results also indicate that facial health positively affects perceived masculinity while facial intelligence negatively affects perceived masculinity, which may partially explain leader choice in some of the environmental contexts. The limitations and a number of implications regarding leadership biases are discussed.

Body height, immunity, facial and vocal attractiveness in young men

Health, facial and vocal attributes and body height of men may affect a diverse range of social outcomes such as attractiveness to potential mates and competition for resources. Despite evidence that each parameter plays a role in mate choice, the relative role of each and inter-relationships between them, is still poorly understood. In this study, we tested relationships both between these parameters and with testosterone and immune function. We report positive relationships between testosterone with facial masculinity and attractiveness, and we found that facial masculinity predicted facial attractiveness and antibody response to a vaccine. Moreover, the relationship between antibody response to a hepatitis B vaccine and body height was found to be non-linear, with a positive relationship up to a height of 188 cm, but an inverse relationship in taller men. We found that vocal attractiveness was dependent upon vocal masculinity. The relationship between vocal attractiveness and body height was also non-linear, with a positive relationship of up to 178 cm, which then decreased in taller men. We did not find a significant relationship between body height and the fundamental frequency of vowel sounds provided by young men, while body height negatively correlated with the frequency of second formant. However, formant frequency was not associated with the strength of immune response. Our results demonstrate the potential of vaccination research to reveal costly traits that govern evolution of mate choice in humans and the importance of trade-offs among these traits.

Facial attractiveness is related to women's cortisol and body fat, but not with immune responsiveness

Recent studies suggest that facial attractiveness indicates immune responsiveness in men and that this relationship is moderated by stress hormones which interact with testosterone levels. However, studies testing whether facial attractiveness in women signals their immune responsiveness are lacking. Here, we photographed young Latvian women, vaccinated them against hepatitis B and measured the amount of specific antibodies produced, cortisol levels and percentage body fat. Latvian men rated the attractiveness of the women's faces. Interestingly, in women, immune responsiveness (amount of antibodies produced) did not predict facial attractiveness. Instead, plasma cortisol level was negatively associated with attractiveness, indicating that stressed women look less attractive. Fat percentage was curvilinearly associated with facial attractiveness, indicating that being too thin or too fat reduces attractiveness. Our study suggests that in contrast to men, facial attractiveness in women does not indicate immune responsiveness against hepatitis B, but is associated with two other aspects of long-term health and fertility: circulating levels of the stress hormone cortisol and percentage body fat.

Adiposity, compared with masculinity, serves as a more valid cue to immunocompetence in human mate choice

According to the 'good genes' hypothesis, females choose males based on traits that indicate the male's genetic quality in terms of disease resistance. The 'immunocompetence handicap hypothesis' proposed that secondary sexual traits serve as indicators of male genetic quality, because they indicate that males can contend with the immunosuppressive effects of testosterone. Masculinity is commonly assumed to serve as such a secondary sexual trait. Yet, women do not consistently prefer masculine looking men, nor is masculinity consistently related to health across studies. Here, we show that adiposity, but not masculinity, significantly mediates the relationship between a direct measure of immune response (hepatitis B antibody response) and attractiveness for both body and facial measurements. In addition, we show that circulating testosterone is more closely associated with adiposity than masculinity. These findings indicate that adiposity, compared with masculinity, serves as a more important cue to immunocompetence in female mate choice.

Cross-cultural variation in women's preferences for cues to sex- and stress-hormones in the male face

Women in the UK prefer the faces of men with low levels of the stress hormone cortisol, and the relationship is moderated by the sex hormone testosterone. In a Latvian sample, however, women's preferences were not affected by cortisol, and the interaction with testosterone differed from that of the UK. To further explore cross-cultural variation in preferences for facial cues to sex- and stress-hormones, we tested the preferences of women from 13 countries for facial composites constructed to differ in combinations of the hormones. We found significant relationships between a measure of societal development (the United Nations human development index 2011) and preferences for cues to testosterone in the face, and the interaction between preferences for cues to testosterone and cortisol. We also found a significant relationship between preferences for cues to testosterone and a societal-level measure of parasite stress. We conclude that societal-level ecological factors influence the relative value of traits revealed by combinations of sex- and stress-hormones.

Evidence for the stress-linked immunocompetence handicap hypothesis in humans

Secondary sexual traits that develop under the action of testosterone, such as masculine human male facial characteristics, have been proposed to signal the strength of the immune system due to the sex hormone's immunosuppressive action. Recent work has suggested that glucocorticoid stress hormones may also influence expression of such sexual signals due to their effects on immune function. Precise roles, however, remain unclear. Here we show positive relationships between testosterone, facial attractiveness and immune function (antibody response to a hepatitis B vaccine) in human males, and present some preliminary evidence that these relationships are moderated by naturally co-occurring cortisol (a glucocorticoid stress hormone involved in the fight-or-flight response). We conclude that our results provide support for a role of glucocorticoids in hormonally mediated sexual selection.

Maternal tendencies in women are associated with estrogen levels and facial femininity

Previous studies have shown that women with higher maternal tendencies are shorter and have lower testosterone levels than those with lower maternal tendencies. Here we report two studies that investigated the relationships between maternal tendencies and two further measures of physical masculinization/feminization; urinary estrogen metabolite (estrone-3-glucuronide: E1-3G) levels (Study 1) and rated facial femininity (Study 2). In Study 1, nulliparous women reported both their ideal number of children and ideal own age at first child and also provided urine samples. There was a significant positive correlation between measured late-follicular estrogen levels and reported ideal number of children. In Study 2, analyses of facial cues in two independent samples of women showed that the average facial characteristics of women who reported desiring many children were rated as more feminine than those desiring fewer children. Collectively, these results support the proposal that maternal tendencies are related to physical feminization and that this effect may, at least in part, reflect the influence of the hormone estrogen.

Cues to sex- and stress-hormones in the human male face: functions of glucocorticoids in the immunocompetence handicap hypothesis

The stress-linked version of the immunocompetence handicap hypothesis has been proposed to account for inconsistencies in relationships between testosterone and immune response. The model has received some support from studies demonstrating roles of stress hormones in relationships between testosterone, immune function and secondary sexual ornamentation. Such work, however, has relied on artificial elevation of testosterone so may not reflect relationships in natural populations. We created human male facial stimuli on the basis of naturally co-occurring levels of salivary testosterone and the stress hormone cortisol. In Study 1 we tested female preferences for male faces with cues to combinations of the hormones across the menstrual cycle, and in Study 2 we tested perceptions of health and dominance in a novel set of facial stimuli. Females preferred cues to low cortisol, a preference that was strongest during the fertile phase of the menstrual cycle. The effects of cortisol on attractiveness and perceived health and dominance were contingent upon level of testosterone: the effects of the stress hormone were reduced when testosterone was high. We propose explanations for our results, including low cortisol as a cue to a heritable component of health, attractiveness as a predictor of low social-evaluative threat (and, therefore, low baseline cortisol) and testosterone as a proxy of male ability to cope efficiently with stressors.

Evidence for the stress-linked immunocompetence handicap hypothesis in human male faces

The stress-linked immunocompetence handicap hypothesis (SL-ICHH) of sexual selection incorporates a role of the stress hormone corticosterone (C; cortisol in humans) in relationships between testosterone (T), immunity and secondary sexual trait expression. In support of this, C has been shown to mediate and moderate relationships between T and immune response and to be inversely related to attractiveness in some avian species. We predicted that female preferences for cues to T in human male faces would be contingent upon co-occurring cortisol levels. In study 1, we tested relationships between T and cortisol and attractiveness, masculinity and health ratings of raw male faces. We found cortisol to be inversely related to attractiveness. In study 2, we tested female preferences for male faces that were parametrically manipulated on the basis of cues to naturally co-occurring levels of T and cortisol across the menstrual cycle. Women preferred cues to low cortisol in general and in the fertile phase of the cycle, and there was an interaction between T and cortisol in general and in the non-fertile phase. Results were consistent with the SL-ICHH but not the original immunocompetence handicap model: females expressed preferences for cues to cortisol but not for cues to T, except in interaction with the stress hormone. Results inform the SL-ICHH by demonstrating female preferences for low cortisol and the nature of its interaction with T in humans, as well as indicating the traits that may be signalled by different combinations of the hormones including immune response, current health and resource acquisition characteristics.

Test of recrudescence hypothesis for overwintering of West Nile virus in gray catbirds

West Nile virus is a pathogen of concern for both human and wildlife health. Although many aspects of the ecology of West Nile virus are well understood, the mechanisms by which this and similar mosquito-borne viruses overwinter and become reinitiated each spring in temperate regions is not known. A thorough understanding of this mechanism is crucial to risk assessment and development of control strategies. One of the hypotheses to explain the mechanism by which this virus persists from year to year is the spring recrudescence of latent virus in avian reservoir hosts. Stress-related immunosuppression is implicated in the recrudescence of latent viruses in birds. We tested the spring recrudescence hypothesis in a controlled laboratory experiment using hatching-year gray catbirds (Dumatella carolinensis) captured in northern Ohio (July-August 2006). Catbirds (n = 60) were experimentally infected (September 2006) and later examined for the effects of immunosuppression through exogenous hormones and artificially induced migratory disposition. We found no effect of either testosterone or migratory behavior on infection status in any of the treatment birds. Moreover, we detected no viral RNA in the kidney, spleen, brain, or liver upon necropsy at 24 wk postinfection.

Daytime micro-naps in a nocturnal migrant: an EEG analysis

Many species of typically diurnal songbirds experience sleep loss during the migratory seasons owing to their nocturnal migrations. However, despite substantial loss of sleep, nocturnally migrating songbirds continue to function normally with no observable effect on their behaviour. It is unclear if and how avian migrants compensate for sleep loss. Recent behavioural evidence suggests that some species may compensate for lost night-time sleep with short, uni- and bilateral 'micro-naps' during the day. We provide electrophysiological evidence that short episodes of sleep-like daytime behaviour (approx. 12s) are accompanied by sleep-like changes in brain activity in an avian migrant. Furthermore, we present evidence that part of this physiological brain response manifests itself as unihemispheric sleep, a state during which one brain hemisphere is asleep while the other hemisphere remains essentially awake. Episodes of daytime sleep may represent a potent adaptation to the challenges of avian migration and offer a plausible explanation for the resilience to sleep loss in nocturnal migrants.

Reproductive strategy, sexual development and attraction to facial characteristics

Sexual reproduction strategies vary both between and within species in the level of investment in offspring. Life-history theories suggest that the rate of sexual maturation is critically linked to reproductive strategy, with high investment being associated with few offspring and delayed maturation. For humans, age of puberty and age of first sex are two developmental milestones that have been associated with reproductive strategies. Stress during early development can retard or accelerate sexual maturation and reproduction. Early age of menarche is associated with absence of younger siblings, absence of a father figure during early life and increased weight. Father absence during early life is also associated with early marriage, pregnancy and divorce. Choice of partner characteristics is critical to successful implementation of sexual strategies. It has been suggested that sexually dimorphic traits (including those evident in the face) signal high-quality immune function and reproductive status. Masculinity in males has also been associated with low investment in mate and offspring. Thus, women's reproductive strategy should be matched to the probability of male investment, hence to male masculinity. Our review leads us to predict associations between the rate of sexual maturation and adult preferences for facial characteristics (enhanced sexual dimorphism and attractiveness). We find for men, engaging in sex at an early age is related to an increased preference for feminized female faces. Similarly, for women, the earlier the age of first sex the greater the preference for masculinity in opposite-sex faces. When we controlled sexual dimorphism in male faces, the speed of sexual development in women was not associated with differences in preference for male facial attractiveness. These developmental influences on partner choice were not mediated by self-rated attractiveness or parental relationships. We conclude that individuals assort in preferences based on the rapidity of their sexual development. Fast developing individuals prefer opposite-sex partners with an increased level of sexually dimorphic facial characteristics.

Facial appearance is a cue to oestrogen levels in women

Although many accounts of facial attractiveness propose that femininity in women's faces indicates high levels of oestrogen, there is little empirical evidence in support of this assumption. Here, we used assays for urinary metabolites of oestrogen (oestrone-3-glucuronide, E1G) and progesterone (pregnanediol-3-glucuronide, P3G) to investigate the relationship between circulating gonadal hormones and ratings of the femininity, attractiveness and apparent health of women's faces. Positive correlations were observed between late follicular oestrogen and ratings of femininity, attractiveness and health. Positive correlations of luteal progesterone and health and attractiveness ratings were marginally significant. Ratings of facial attributions did not relate to hormone levels for women wearing make-up when photographed. There was no effect of sex of rater on the relationships between oestrogen and ratings of facial appearance. These findings demonstrate that female facial appearance holds detectable cues to reproductive health that are considered attractive by other people.

Menstrual cycle, trait estrogen level, and masculinity preferences in the human voice

Men with low testosterone (feminine men) invest in relationships and offspring more than men with high testosterone (masculine men). Women's attraction to testosterone dependent traits (e.g. masculine face shape) is enhanced during the late-follicular, fertile phase of the menstrual cycle. Attractive, feminine women have stronger preferences for masculine men as possible long-term partners than less attractive, masculine women. We manipulated 2 testosterone related vocal traits (voice pitch and apparent vocal-tract length) in voices to test if women prefer masculinized men's voices to feminized men's voices; masculinity preferences are enhanced at the fertile (late-follicular) menstrual cycle phase; the amount that masculinity preferences shift cyclically relates to average estrone-3-glucuronide concentration (the primary urinary metabolite of estrone, E3G). We found women displayed general masculinity preferences for men's voices; masculinity preferences were greater in the fertile (late-follicular) phase of the cycle than the non-fertile (early-follicular and luteal) phase; and this effect was most pronounced for women with low average E3G concentration. As feminine women (i.e. those with high average E3G levels) are most able to obtain investment even from masculine men, these women may not need to change their mating preference or strategy during the menstrual cycle as much as masculine women.

Commitment to relationships and preferences for femininity and apparent health in faces are strongest on days of the menstrual cycle when progesterone level is high

Previous studies of changes in women's behavior during the menstrual cycle have offered insight into the motivations underpinning women's preferences for social cues associated with possible direct benefits (e.g., investment, low risk of infection) and indirect benefits (e.g., offspring viability). Here we sought to extend this work by testing for systematic variation in women's preferences for male and female faces and in their attitudes to their romantic relationship during the menstrual cycle. In Study 1, we found partnered women's reported commitment to their romantic relationship and preferences for femininity in male and female faces were strongest on days of the menstrual cycle when progesterone levels are increased (and fertility is low). Happiness in relationships did not change across the cycle. In Study 2, we found that the effect of cycle phase on women's preference for feminine faces was independent of increased attraction to apparent health in faces during the luteal phase. Collectively, these findings are further evidence that women's preferences for social cues associated with possible direct benefits and commitment to relationships are strongest during conditions characterized by raised progesterone level, while attraction to men displaying cues associated with possible indirect benefits is strongest when women are most fertile.

Menstrual cycle, pregnancy and oral contraceptive use alter attraction to apparent health in faces

Previous studies demonstrating changes in women's face preferences have emphasized increased attraction to cues to possible indirect benefits (e.g. heritable immunity to infection) that coincides with periods of high fertility (e.g. the late follicular phase of the menstrual cycle). By contrast, here we show that when choosing between composite faces with raised or lowered apparent health, women's preferences for faces that are perceived as healthy are (i) stronger during the luteal phase of the menstrual cycle than during the late follicular, fertile phase, (ii) stronger in pregnant women than in non-pregnant women and (iii) stronger in women using oral contraceptives than in women with natural menstrual cycles. Change in preference for male faces was greater for short- than long-term relationships. These findings indicate raised progesterone level is associated with increased attraction to facial cues associated with possible direct benefits (e.g. low risk of infection) and suggest that women's face preferences are influenced by adaptations that compensate for weakened immune system responses during pregnancy and reduce the risk of infection disrupting foetal development.

Histopathologic types of benign breast lesions and the risk of breast cancer: case-control study

The hypothetical multistep model of carcinogenesis indicates that breast cancer develops via a series of intermediate hyperplastic lesions through in situ to invasive carcinoma. To identify the risk inherent within the different morphologic lesions, we have analyzed the data from 674 benign biopsy specimens comprising 120 cases who subsequently developed breast cancer and 382 controls (matched for age and date of biopsy) spanning a period up to 20 years of follow-up (mean 66.95 months). In this series we have confirmed an increased risk associated with certain types of benign breast lesions. Atypical lobular hyperplasia was the most significant risk factor for breast cancer with more unfavorable outcome in patients <50 years of age (p = 0.003) and a relative risk (RR) of 4.55 (confidence interval [CI] 1.77-11.69). Hyperplasia of usual type showed an RR of 1.53 (CL 1.10-2.13) with a statistically worse probability of survival (cancer-free time) for patients >50 years. For atypical ductal hyperplasia the RR was 2.03 (CI 0.80-1.39). Blunt duct adenosis was significantly more common in cases progressing to breast cancer compared with controls, showing an RR of 2.08 (CI 1.12-2.85). We describe in detail the criteria of morphologic changes observed in blunt duct adenosis and define, for the first time, the level of risk associated with each of its six subtypes. Improved knowledge of breast carcinogenesis will provide insight for defining high-risk groups thus resulting in improved screening and management regimens.

Magnetic information calibrates celestial cues during migration

Migratory birds use celestial and geomagnetic directional information to orient on their way between breeding and wintering areas. Cue-conflict experiments involving these two orientation cue systems have shown that directional information can be transferred from one system to the other by calibration. We designed experiments with four species of North American songbirds to: (1) examine whether these species calibrate orientation information from one system to the other; and (2) determine whether there are species-specific differences in calibration. Migratory orientation was recorded with two different techniques, cage tests and free-flight release tests, during autumn migration. Cage tests at dusk in the local geomagnetic field revealed species-specific differences: red-eyed vireo, Vireo olivaceus, and northern waterthrush, Seiurus noveboracensis, selected seasonally appropriate southerly directions whereas indigo bunting, Passerina cyanea, and grey catbird, Dumetella carolinensis, oriented towards the sunset direction. When tested in deflected magnetic fields, vireos and waterthrushes responded by shifting their orientation according to the deflection of the magnetic field, but buntings and catbirds failed to show any response to the treatment. In release tests, all four species showed that they had recalibrated their star compass on the basis of the magnetic field they had just experienced in the cage tests. Since release tests were done in the local geomagnetic field it seems clear that once the migratory direction is determined, most likely during the twilight period, the birds use their recalibrated star compass for orientation at departure. Copyright 2000 The Association for the Study of Animal Behaviour.

Genotoxicity evaluation of selenium sulfide in in vivo and in vivo/in vitro micronucleus and chromosome aberration assays

Selenium monosulfide (SeS) was reported to be carcinogenic to livers of male and female rats and livers and lungs of female mice. However, its genotoxicity profile in short-term assays is somewhat equivocal. A multiple endpoint/multiple tissue approach to short-term genetic toxicity testing has been developed in our laboratory. In the present paper, the effect of SeS in in vivo and in vivo/in vitro micronucleus and chromosome aberration assays in rat bone marrow and spleen are reported. In the in vivo assay, small but statistically significant increases in bone marrow micronucleated polychromatic erythrocytes (MNPCEs) were observed 24 h after treatment of rats with 50 mg/kg SeS and 48 h after treatment with 12.5 mg/kg. A significant decrease in the PCE/total erythrocyte (TE) ratio, indicative of cytotoxicity, was observed at the 50 mg/kg dose at the 24-h timepoint. In spleen, no increases in MNPCEs or decreases in the PCE/TE ratios were observed. No evidence of a significant increase in aberrations was observed in bone marrow or spleen. In the in vivo/in vitro assay, no increase in micronucleated binucleated cells or cells with aberrations was observed in SeS-treated rats. The small but statistically significant increases in MN observed in the in vivo study are considered likely not to be biologically significant since no dose-response was observed and all the values obtained were within historical control range in our laboratory. Given the overall genetic toxicity profile of SeS, it appears that SeS may be a weak mutagen and that differences between testing protocols may be very important in determining whether or not it is found to be negative or positive. Histological evidence was obtained in this study that suggests that the liver is the acute target organ of SeS in rats. Given the fact that SeS is selectively hepatocarcinogenic, we are currently testing the hypothesis that the genotoxicity of SeS in rats may be more readily detectable in liver than in bone marrow or spleen.

An in vivo/in vitro method for assessing micronucleus and chromosome aberration induction in rat bone marrow and spleen. 2. Studies with chlorambucil and mitomycin C

An in vivo/in vitro system using rat bone marrow cells and spleen cells to assess micronucleus (MN) and structural chromosome aberrations (SCA) simultaneously (Moore et al., 1995) was further developed. In two separate experiments, two rats/dose/experiment were treated i.p. with 0, 5, 10 and 15 mg chlorambucil (CA)/kg or with mitomycin C (MMC) at 0, 1, 2, 4 mg/kg (experiment 1) or 0, 4, 6, and 8 mg/kg (experiment 2) and killed 6 h later. Cultures were then established in the presence of growth stimulants (interleukin-3 and granulocyte-macrophage colony stimulating factor for bone marrow; lipopolysaccharide and concanavalin A for spleen) and cytochalasin B, a cytokinesis inhibitor. Bone marrow cells were harvested 24 h after establishment of cultures, while spleen cells were harvested at 48 h. In addition, spleen cells were concurrently assayed for chromosome aberrations. With the MN endpoint, spleen cells appeared more sensitive than bone marrow cells to the effects of CA due both to a lower background and an increased response. For MMC, bone marrow cells exhibited both a higher background of MN and a greater numerical response than did spleen cells. However, on the basis of a fold-increase over control values, spleen cells were more sensitive than bone marrow cells. In general, the MN endpoint appeared more sensitive than the SCA in spleen cells after treatment with CA or MMC. Thus, the approach described here shows greater potential in detecting genotoxicity.

An in vivo/in vitro method for assessing micronucleus and chromosome aberration induction in rat bone marrow and spleen. 1. Studies with cyclophosphamide

The mouse micronucleus assay has long been used as an indicator of in vivo genotoxicity. Recently, it was shown that no single protocol is adequate to detect all clastogens. As a first step in developing a potentially more sensitive assay, micronucleus induction by cyclophosphamide (CP) was assessed in an in vivo/in vitro system using rat bone marrow and spleen cells. In each of two independent experiments, two rats/dose were treated i.p. with 0, 20, or 40 mg CP/kg and killed 6 h later. Cultures were then established in the presence of growth stimulants (interleukin-3 and granulocyte-macrophage colony stimulating factor for bone marrow; lipopolysaccharide and concanavalin A for spleen) and cytochalasin B, a cytokinesis inhibitor. Bone marrow cells were harvested and slides prepared 24 h after initiation, while spleen cells were harvested at 48 h. One thousand cells/tissue/group were scored for cell cycle kinetics and 1000 binucleate (BN) cells were scored for micronuclei. In addition, spleen cells were concurrently assayed for chromosome aberrations. A dose-related cell cycle delay was observed in both tissues in both experiments. Bone marrow showed a 6% average background frequency of micronucleated BN cells, while the low dose induced an average of 20%, and the high dose 31%. For spleen, the average control frequency of micronucleated BN cells was 3%, the low dose induced a 40% average frequency, and the high dose 65%. Also in splenocytes, a dose-dependent increase in chromosome aberrations was observed, with an almost 40-fold increase observed over the control value at the high dose. Thus, the in vivo/in vitro approach described here shows great potential in detecting drug induced genotoxicity. Also, spleen appears more sensitive than bone marrow to CP.

Cytogenetic studies of cell lines derived from Marek's disease virus-induced local lesions

Cytogenetic analysis of cell lines derived from Marek's disease virus (MDV) induced local lesions was performed to detect the presence of a chromosomal alteration found previously in cell lines derived from MDV-induced visceral tumors. This chromosomal alteration involves an amplified region on the short arm of chromosome 1. Trypsin G-binding was performed on 12 local-lesion cell lines having various T-cell receptor phenotypes. Eight of 12 cell lines had a diploid female karyotype, and four lines were diploid males. Ten of the cell lines showed a normal G-banding pattern; two lines, however, had the short arm amplification on chromosome 1 (1p+). Thus, the 1p+ alteration does not appear to be necessary for establishment of cell lines from local lesions. The occurrence of the 1p+ alteration in Marek's disease cell lines suggests a possible role for this alteration in late stages of multi-step viral oncogenesis.

Consistent chromosomal aberration in cell lines transformed with Marek's disease herpesvirus: evidence of genomic DNA amplification

A specific chromosomal aberration was observed in 14 of 15 avian lymphoblastoid cell lines transformed with Marek's disease herpesvirus. This aberration, designated dup(1p)(p22-p23), appeared as an extra G-positive band and interband on the short arm of one chromosome I homolog. Using fluorescent in situ hybridization, we identified amplified genomic DNA sequences in this region. This amplification involves sequences linked to an endogenous retrovirus locus and genes in the histone multigene family. This aberration was not observed in cells transformed by reticuloendotheliosis virus or by avian leukosis virus, nor has it been observed in untransformed chicken cells. The induction of the 1p+ chromosomal aberration may be an essential event in the transformation of lymphocytes by Marek's disease virus.

Social interactions among rodent conspecifics: a review of experimental paradigms

The authors suggest that kin selection theory offers a different perspective from which to examine social interactions among rodent conspecifics. Paradigms designed to investigate various interactions among rodent conspecifics are presented, and include simple affiliative behaviors, social facilitation, and cooperation. It is established that many species of rodents are appropriately social to use as subjects under investigation in research which focuses on topics such as kin selection. Studies reporting positive results as well as some reporting negative or inconclusive results have been presented for the purpose of informing the reader under which conditions we might expect specific social behaviors to occur. It is concluded that a combined method of a sociobiological perspective using established experimental procedures will offer unique opportunities for the investigation of specific predictions suggested by kin selection theory.

Responses of albino rats to distress of littermates and nonfamiliar agemates

It was hypothesized that the pain or distress of littermates would yield higher levels of stress-indicators (urinations and defecations) in rats than the pain or distress of nonfamiliar agemates. Albino rats were exposed to the shock of biological littermates, cross-fostered littermates, biological siblings reared in another litter, and unfamiliar agemates. Statistical analysis indicated that, when the subjects were exposed to the shock of biological littermates, urinations and defecations were more frequent than when the subjects were exposed to the shock of the other animals.

Geomagnetic disturbance and the orientation of nocturnally migrating birds

Free-flying passerine migrants respond to natural fluctuations in the earth's magnetic field. The variability in flight directions of nocturnal migrants is significantly correlated with increasing geomagnetic disturbance as measured by both the K index and various components of the earth's magnetic field. The results indicate that such disturbances influence the orientation of free-flying migrants, but the evidence is not sufficient to show that geomagnetism is a cue in their orientation system.