Specialization Does Not Predict Individual Efficiency in an Ant

The ecological success of social insects is often attributed to an increase in efficiency achieved through division of labor between workers in a colony. Much research has therefore focused on the mechanism by which a division of labor is implemented, i.e., on how tasks are allocated to workers. However, the important assumption that specialists are indeed more efficient at their work than generalist individuals—the “Jack-of-all-trades is master of none” hypothesis—has rarely been tested. Here, I quantify worker efficiency, measured as work completed per time, in four different tasks in the ant Temnothorax albipennis: honey and protein foraging, collection of nest-building material, and brood transports in a colony emigration. I show that individual efficiency is not predicted by how specialized workers were on the respective task. Worker efficiency is also not consistently predicted by that worker''s overall activity or delay to begin the task. Even when only the worker''s rank relative to nestmates in the same colony was used, specialization did not predict efficiency in three out of the four tasks, and more specialized workers actually performed worse than others in the fourth task (collection of sand grains). I also show that the above relationships, as well as median individual efficiency, do not change with colony size. My results demonstrate that in an ant species without morphologically differentiated worker castes, workers may nevertheless differ in their ability to perform different tasks. Surprisingly, this variation is not utilized by the colony—worker allocation to tasks is unrelated to their ability to perform them. What, then, are the adaptive benefits of behavioral specialization, and why do workers choose tasks without regard for whether they can perform them well? We are still far from an understanding of the adaptive benefits of division of labor in social insects.     

Race Does Not Predict Melanocyte Heterogeneous Responses to Dermal Fibroblast-Derived Mediators

Introduction

Abnormal pigmentation following cutaneous injury causes significant patient distress and represents a barrier to recovery. Wound depth and patient characteristics influence scar pigmentation. However, we know little about the pathophysiology leading to hyperpigmentation in healed shallow wounds and hypopigmentation in deep dermal wound scars. We sought to determine whether dermal fibroblast signaling influences melanocyte responses.

Methods and Materials

Epidermal melanocytes from three Caucasians and three African-Americans were genotyped for single nucleotide polymorphisms (SNPs) across the entire genome. Melanocyte genetic profiles were determined using principal component analysis. We assessed melanocyte phenotype and gene expression in response to dermal fibroblast-conditioned medium and determined potential mesenchymal mediators by proteome profiling the fibroblast-conditioned medium.

Results

Six melanocyte samples demonstrated significant variability in phenotype and gene expression at baseline and in response to fibroblast-conditioned medium. Genetic profiling for SNPs in receptors for 13 identified soluble fibroblast-secreted mediators demonstrated considerable heterogeneity, potentially explaining the variable melanocyte responses to fibroblast-conditioned medium.

Discussion

Our data suggest that melanocytes respond to dermal fibroblast-derived mediators independent of keratinocytes and raise the possibility that mesenchymal-epidermal interactions influence skin pigmentation during cutaneous scarring.     

Breast Cancer Cell Line Aggregate Morphology Does Not Predict Invasive Capacity

To invade and metastasize to distant loci, breast cancer cells must breach the layer of basement membrane surrounding the tumor and then invade through the dense collagen I-rich extracellular environment of breast tissue. Previous studies have shown that breast cancer cell aggregate morphology in basement membrane extract correlated with cell invasive capacity in some contexts. Moreover, cell lines from the same aggregate morphological class exhibited similarities in gene expression patterns. To further assess the capacity of cell and aggregate morphology to predict invasive capacity in physiologically relevant environments, six cell lines with varied cell aggregate morphologies were assessed in a variety of assays including a 3D multicellular invasion assay that recapitulates cell-cell and cell-environment contacts as they exist in vivo in the context of the primary breast tumor. Migratory and invasive capacities as measured through a 2D gap assay and a 3D spheroid invasion assay reveal that breast cancer cell aggregate morphology alone is insufficient to predict migratory speed in 2D or invasive capacity in 3D. Correlations between the 3D spheroid invasion assay and gene expression profiles suggest this assay as an inexpensive functional method to predict breast cancer invasive capacity.     

The Impact of Menstrual Cycle Phase on Economic Choice and Rationality

It is well known that hormones affect both brain and behavior, but less is known about the extent to which hormones affect economic decision-making. Numerous studies demonstrate gender differences in attitudes to risk and loss in financial decision-making, often finding that women are more loss and risk averse than men. It is unclear what drives these effects and whether cyclically varying hormonal differences between men and women contribute to differences in economic preferences. We focus here on how economic rationality and preferences change as a function of menstrual cycle phase in women. We tested adherence to the Generalized Axiom of Revealed Preference (GARP), the standard test of economic rationality. If choices satisfy GARP then there exists a well-behaved utility function that the subject’s decisions maximize. We also examined whether risk attitudes and loss aversion change as a function of cycle phase. We found that, despite large fluctuations in hormone levels, women are as technically rational in their choice behavior as their male counterparts at all phases of the menstrual cycle. However, women are more likely to choose risky options that can lead to potential losses while ovulating; during ovulation women are less loss averse than men and therefore more economically rational than men in this regard. These findings may have market-level implications: ovulating women more effectively maximize expected value than do other groups.     

Pancreatitis-Associated Protein Does Not Predict Disease Relapse in Inflammatory Bowel Disease Patients

Background

The pancreatitis-associated protein (PAP) is increased in the serum of active inflammatory bowel disease (IBD) patients and its levels seem to be correlated with disease activity. Our aim was to evaluate the usefulness of serum and fecal PAP measurements to predict relapse in patients with inactive IBD.

Materials and Methods

We undertook a 12-month prospective study that included 66 Crohn''s disease (CD) and 74 ulcerative colitis (UC) patients. At inclusion, patients were in clinical remission, defined by a Harvey-Bradshaw (HB) Index≤4 (CD) or a partial Mayo Score (MS)<3 (UC), along with a normal serum C reactive protein (CRP) and fecal calprotectin. Patients were followed every 3 months. Blood and stool samples were collected and a clinical evaluation was performed at each visit. Serum PAP and CRP levels as well as fecal concentrations of PAP and calprotectin were assessed.

Results

Active CD patients had an increased mean serum PAP at the diagnosis of the flare (104.1 ng/ml) and 3 months prior to activity (22.68 ng/ml) compared with patients in remission (13.26 ng/ml), p<0.05. No significant change in serum PAP levels in UC and fecal PAP levels in CD and UC were detected during disease activity. In CD, serum PAP was a poor diagnostic predictor of disease activity, with an AUC of 0.69. In patients in remission, fecal PAP was barely detectable in UC compared with CD patients.

Conclusion

Serum PAP is increased only in active CD patients, but this marker does not predict disease activity. Inactive UC patients have marked low levels of PAP in fecal samples compared with CD patients.     

Coordinate-Based Lead Location Does Not Predict Parkinson's Disease Deep Brain Stimulation Outcome

Background

Effective target regions for deep brain stimulation (DBS) in Parkinson''s disease (PD) have been well characterized. We sought to study whether the measured Cartesian coordinates of an implanted DBS lead are predictive of motor outcome(s). We tested the hypothesis that the position and trajectory of the DBS lead relative to the mid-commissural point (MCP) are significant predictors of clinical outcomes. We expected that due to neuroanatomical variation among individuals, a simple measure of the position of the DBS lead relative to MCP (commonly used in clinical practice) may not be a reliable predictor of clinical outcomes when utilized alone.

Methods

55 PD subjects implanted with subthalamic nucleus (STN) DBS and 41 subjects implanted with globus pallidus internus (GPi) DBS were included. Lead locations in AC-PC space (x, y, z coordinates of the active contact and sagittal and coronal entry angles) measured on high-resolution CT-MRI fused images, and motor outcomes (Unified Parkinson''s Disease Rating Scale) were analyzed to confirm or refute a correlation between coordinate-based lead locations and DBS motor outcomes.

Results

Coordinate-based lead locations were not a significant predictor of change in UPDRS III motor scores when comparing pre- versus post-operative values. The only potentially significant individual predictor of change in UPDRS motor scores was the antero-posterior coordinate of the GPi lead (more anterior lead locations resulted in a worse outcome), but this was only a statistical trend (p<.082).

Conclusion

The results of the study showed that a simple measure of the position of the DBS lead relative to the MCP is not significantly correlated with PD motor outcomes, presumably because this method fails to account for individual neuroanatomical variability. However, there is broad agreement that motor outcomes depend strongly on lead location. The results suggest the need for more detailed identification of stimulation location relative to anatomical targets.     

Hemispheric Specialization Varies with EEG Brain Resting States and Phase of Menstrual Cycle

A growing body of behavioral studies has demonstrated that women’s hemispheric specialization varies as a function of their menstrual cycle, with hemispheric specialization enhanced during their menstruation period. Our recent high-density electroencephalogram (EEG) study with lateralized emotional versus neutral words extended these behavioral results by showing that hemispheric specialization in men, but not in women under birth-control, depends upon specific EEG resting brain states at stimulus arrival, suggesting that hemispheric specialization may be pre-determined at the moment of the stimulus onset. To investigate whether EEG brain resting state for hemispheric specialization could vary as a function of the menstrual phase, we tested 12 right-handed healthy women over different phases of their menstrual cycle combining high-density EEG recordings and the same lateralized lexical decision paradigm with emotional versus neutral words. Results showed the presence of specific EEG resting brain states, associated with hemispheric specialization for emotional words, at the moment of the stimulus onset during the menstruation period only. These results suggest that the pre-stimulus EEG pattern influencing hemispheric specialization is modulated by the hormonal state.     

Tryptophan Metabolism During the Menstrual Cycle

The metabolism of tryptophan and tryptophan metabolites was investigated during the follicular, luteal and premenstrual phases of the menstrual cycle in 33 healthy women across one cycle. The metabolites of all three pathways of tryptophan ie the serotonergic pathway, the pyrollase pathway and the indole acetic acid pathway, were assayed from urinary prebreakfast samples collected on a repeated measures basis. Urinary 3 hydroxy kynurenine excretion was significantly elevated in the luteal phase (p=0.030). The relative activity of the serotonergic pathway to the kynurenergic pathway (identified by the ratios 5HT+HIAA/KY+HK and 5HT/KY+HK) were significantly elevated in both the luteal and premenstrual phases compared to the follicular phase (p=0.009 and p=0.005 respectively); indicating that the kynurenergic pathway of tryptophan metabolism may modulate serotonergic metabolism (via HK) during the menstrual cycle; and that the relative and not actual levels of serotonin metabolism may be the important factor when investigating any cyclical effects of the neurotransmitter serotonin.     

Tryptophan Metabolism During the Menstrual Cycle

The metabolism of tryptophan and tryptophan metabolites was investigated during the follicular, luteal and premenstrual phases of the menstrual cycle in 33 healthy women across one cycle. The metabolites of all three pathways of tryptophan ie the serotonergic pathway, the pyrollase pathway and the indole acetic acid pathway, were assayed from urinary prebreakfast samples collected on a repeated measures basis. Urinary 3 hydroxy kynurenine excretion was significantly elevated in the luteal phase (p=0.030). The relative activity of the serotonergic pathway to the kynurenergic pathway (identified by the ratios 5HT+HIAA/KY+HK and 5HT/KY+HK) were significantly elevated in both the luteal and premenstrual phases compared to the follicular phase (p=0.009 and p=0.005 respectively); indicating that the kynurenergic pathway of tryptophan metabolism may modulate serotonergic metabolism (via HK) during the menstrual cycle; and that the relative and not actual levels of serotonin metabolism may be the important factor when investigating any cyclical effects of the neurotransmitter serotonin.     

Effect of Sex, Menstrual Cycle Phase, and Oral Contraceptive Use on Circadian Temperature Rhythms

The circadian rhythm of rectal temperature was continuously recorded over several consecutive days in young men and women on regular nocturnal sleep schedules. There were 50 men, 21 women with natural menstrual cycles [i.e., not taking oral contraceptives (OCs) (10 in the follicular phase and 11 in the luteal phase)], and 14 women using OCs (6 in the pseudofollicular phase and 8 in the pseudoluteal phase). Circadian phase and amplitude were estimated using a curve-fitting procedure, and temperature levels were determined from the raw data. A two-way analysis of variance (ANOVA) on the data from the four groups of women, with factors menstrual cycle phase (follicular, luteal) and OC use (yes, no), showed that temperature during sleep was lower during the follicular phase than during the luteal phase. Since waking temperatures were similar in the two phases, the circadian amplitude was also larger during the follicular phase. The lower follicular phase sleep temperature also resulted in a lower 24-h temperature during the follicular phase. The two-way ANOVA showed that temperature during sleep and 24-h temperature were lower in naturally cycling women than in women taking OCs. A one-way ANOVA on the temperature rhythm parameters from the five groups of subjects showed that the temperature rhythms of the men and of the naturally cycling women in the follicular phase were not significantly different. Both of these groups had lower temperatures during sleep, lower 24-h temperatures, and larger circadian amplitudes than the other groups. There were no significant differences in circadian phase among the five groups studied. In conclusion, menstrual cycle phase, OC use, and sex affect the amplitude and level, but not the phase, of the overt circadian temperature rhythm.     

Differences in the Relationship of Menstrual Cycle Phase to Spatial Performance on Two- and Three-Dimensional Tasks

Inverse activational effects of estrogen on spatial problem-solving performance in females have been amply demonstrated, although the findings across studies are somewhat inconsistent. In an attempt to resolve this ambiguity, the present study compared activational effects, using phases of the menstrual cycle as the criteria for estrogen levels, on two- and three-dimensional spatial tasks. As predicted, menstrual cycle effects were obtained for the latter category only. Results were interpreted as a function of the greater ecological validity of three-dimensional tasks.     

The Effects of Menstrual Cycle on Dreaming

In this study we have investigated the effect that the menstrual cycle has on dreams, sleep quality and mood. A total of 16 women, university students, with a regular menstrual cycle of 28 days, not on any form of hormonal treatment were tested over five weeks. Methods of diary of dreams, daily self-evaluation of mood and weekly self-assessment of quality of sleep were adopted. Mood scores varied significantly during the menstrual cycle (p &lt; 0.05) with improvement of mood around the time of ovulation and worsening during the pre-menstrual phase of the cycle. Sleep quality did not vary significantly during the menstrual cycle. During the pre-ovulatory phase of the cycle dreams had the highest levels of incongruity (p &lt; 0.05), number of positive emotions (p &lt; 0.0005), number of male-non-self-characters (p &lt; 0.005) and erotic content (p &lt; 0.001). While during the pre-menstrual phase dreams were longer (p &lt; 0.05) and with a larger number of female characters (p &lt; 0.005) and of negative emotions (p &lt; 0.0005). These results suggest that the hormonal variations during the menstrual cycle may have an effect on dreaming. Both the preovulatory oestrogen peak and the presence of progesterone during the luteal phase may enhance memory processes involved in the dream production.     

Effect of Sex,Menstrual Cycle Phase,and Oral Contraceptive Use on Circadian Temperature Rhythms

The circadian rhythm of rectal temperature was continuously recorded over several consecutive days in young men and women on regular nocturnal sleep schedules. There were 50 men, 21 women with natural menstrual cycles [i.e., not taking oral contraceptives (OCs) (10 in the follicular phase and 11 in the luteal phase)], and 14 women using OCs (6 in the pseudofollicular phase and 8 in the pseudoluteal phase). Circadian phase and amplitude were estimated using a curve-fitting procedure, and temperature levels were determined from the raw data. A two-way analysis of variance (ANOVA) on the data from the four groups of women, with factors menstrual cycle phase (follicular, luteal) and OC use (yes, no), showed that temperature during sleep was lower during the follicular phase than during the luteal phase. Since waking temperatures were similar in the two phases, the circadian amplitude was also larger during the follicular phase. The lower follicular phase sleep temperature also resulted in a lower 24-h temperature during the follicular phase. The two-way ANOVA showed that temperature during sleep and 24-h temperature were lower in naturally cycling women than in women taking OCs. A one-way ANOVA on the temperature rhythm parameters from the five groups of subjects showed that the temperature rhythms of the men and of the naturally cycling women in the follicular phase were not significantly different. Both of these groups had lower temperatures during sleep, lower 24-h temperatures, and larger circadian amplitudes than the other groups. There were no significant differences in circadian phase among the five groups studied. In conclusion, menstrual cycle phase, OC use, and sex affect the amplitude and level, but not the phase, of the overt circadian temperature rhythm.