Social bonds facilitate cooperative resource sharing in wild chimpanzees.

Why share when access to benefits is uncertain is crucial to our understanding of the evolution of humans' extensive cooperation. Here, we investigated some of the different human sharing hypotheses and potential neuroendocrine mechanisms, in one of our closest living relatives, chimpanzees. The strongest predictor of sharing across food types was the presence of enduring and mutually preferred grooming partners, more than harassment, direct signalling, or trade. Moreover, urinary oxytocin levels were higher after the sharing of both individually and jointly acquired resources compared with controls. We conclude that the emotional connection inherent in social bonds was a key factor determining sharing patterns, with the oxytocinergic system potentially facilitating long-term cooperative exchanges. Testing for the role of social bonds in increasing predictability of sharing behaviour, a feature frequently overlooked, may help us to identify the evolutionary drivers of resource sharing and mechanisms that sustain delayed reciprocity between non-kin.

Urinary oxytocin levels in relation to post-conflict affiliations in wild male chimpanzees (Pan troglodytes verus).

Many animals living in social groups have evolved behaviors to resolve conflicts between group members, behaviors thought crucial for maintaining stable group life. Several hypotheses, based mainly on observational data, aim to explain how post-conflict (PC) affiliations, such as reconciliation and consolation, resolve conflicts by restoring relationships and/or alleviating anxiety. To examine a potential endocrinological mechanism of PC affiliations, we used an experimental-like procedure to investigate whether the oxytocinergic system is activated during naturally observed reconciliations, receiving bystander PC affiliations and aggressions not followed by PC affiliations in wild male chimpanzees. We compared urinary oxytocin (uOT) levels after reconciliations, receiving bystander PC affiliations or aggressions without affiliations with two control conditions: affiliations without previous aggression and after time periods without social interactions. We furthermore tested the 'valuable relationship' hypothesis of reconciliation, as well as the influence of relationship quality between individuals engaged in each of the three behavioral conditions involving aggression on uOT levels. We found that the probability to reconcile a conflict increased with increasing relationship quality between opponents, thus our results support the 'valuable relationship' hypothesis. However, relationship quality did not influence uOT levels, while behavioral condition had a significant effect on uOT levels. uOT levels after reconciliations, receiving bystander PC affiliations and affiliations not related to conflicts were higher than after aggressions alone and time periods without social interactions. Overall, our results indicate that the oxytocinergic system is activated during affiliative interactions, whether occurring as reconciliation, bystander PC affiliation or affiliation alone. We conclude that the oxytocinergic system, in addition to building and maintaining social relationships, also takes part in repairing them.

Functional host-specific adaptation of the intestinal microbiome in hominids.

Fine-scale knowledge of the changes in composition and function of the human gut microbiome compared that of our closest relatives is critical for understanding the evolutionary processes underlying its developmental trajectory. To infer taxonomic and functional changes in the gut microbiome across hominids at different timescales, we perform high-resolution metagenomic-based analyzes of the fecal microbiome from over two hundred samples including diverse human populations, as well as wild-living chimpanzees, bonobos, and gorillas. We find human-associated taxa depleted within non-human apes and patterns of host-specific gut microbiota, suggesting the widespread acquisition of novel microbial clades along the evolutionary divergence of hosts. In contrast, we reveal multiple lines of evidence for a pervasive loss of diversity in human populations in correlation with a high Human Development Index, including evolutionarily conserved clades. Similarly, patterns of co-phylogeny between microbes and hosts are found to be disrupted in humans. Together with identifying individual microbial taxa and functional adaptations that correlate to host phylogeny, these findings offer insights into specific candidates playing a role in the diverging trajectories of the gut microbiome of hominids. We find that repeated horizontal gene transfer and gene loss, as well as the adaptation to transient microaerobic conditions appear to have played a role in the evolution of the human gut microbiome.

Urinary oxytocin and social bonding in related and unrelated wild chimpanzees.

Animals that maintain cooperative relationships show gains in longevity and offspring survival. However, little is known about the cognitive or hormonal mechanisms involved in cooperation. Indeed, there is little support for a main hypothesis that non-human animals have the cognitive capacities required for bookkeeping of cooperative exchanges. We tested an alternative hypothesis that cooperative relationships are facilitated by an endocrinological mechanism involving oxytocin, a hormone required for bonding in parental and sexual relationships across mammals. We measured urinary oxytocin after single bouts of grooming in wild chimpanzees. Oxytocin levels were higher after grooming with bond partners compared with non-bond partners or after no grooming, regardless of genetic relatedness or sexual interest. We ruled out other possible confounds, such as grooming duration, grooming direction or sampling regime issues, indicating that changes in oxytocin levels were mediated by social bond strength. Oxytocin, which is thought to act directly on neural reward and social memory systems, is likely to play a key role in keeping track of social interactions with multiple individuals over time. The evolutionary linkage of an ancestral hormonal system with complex social cognition may be the primary mechanism through which long-term cooperative relationships develop between both kin and non-kin in mammals.

Light exposure and cell viability in fluorescence microscopy.

Test systems for measuring cell viability in optical microscopy (based on colony formation ability or lysosomal integrity) were established and applied to native cells as well as to cells incubated with fluorescence markers or transfected with genes encoding for fluorescent proteins. Human glioblastoma and Chinese hamster ovary cells were irradiated by various light doses, and maximum doses where at least 90% of the cells survived were determined. These tolerable light doses were in the range between 25 J cm⁻² and about 300 J cm⁻² for native cells (corresponding to about 250-3000 s of solar irradiance and depending on the wavelength as well as on the mode of illumination, e.g. epi- or total internal reflection illumination) and decreased to values between 50 J cm⁻² and less than 1 J cm⁻² upon application of fluorescent markers, fluorescent proteins or photosensitizers. In high-resolution wide field or laser scanning microscopy of single cells, typically 10-20 individual cell layers needed for reconstruction of a 3D image could be recorded with tolerable dose values. Tolerable light doses were also maintained in fluorescence microscopy of larger 3D samples, e.g. cell spheroids exposed to structured illumination, but may be exceeded in super-resolution microscopy based on single molecule detection.

Stratigraphy of stable isotope ratios and leaf structure within an African rainforest canopy with implications for primate isotope ecology.

The canopy effect describes vertical variation in the isotope ratios of carbon (δ13C), oxygen (δ18O) and partially nitrogen (δ15N) within plants throughout a closed canopy forest, and may facilitate the study of canopy feeding niches in arboreal primates. However, the nuanced relationship between leaf height, sunlight exposure and the resulting variation in isotope ratios and leaf mass per area (LMA) has not been documented for an African rainforest. Here, we present δ13C, δ18O and δ15N values of leaves (n = 321) systematically collected from 58 primate food plants throughout the canopy (0.3 to 42 m) in Côte d'Ivoire, West Africa. Besides leaf sample height and light availability, we measured leaf nitrogen and carbon content (%N, %C), as well as LMA (n = 214) to address the plants' vertical resource allocations. We found significant variation in δ13C, δ18O and δ15N, as well as LMA in response to height in combination with light availability and tree species, with low canopy leaves depleted in 13C, 18O and 15N and slightly higher in %N compared to higher canopy strata. While this vertical isotopic variation was not well reflected in the δ13C and δ15N of arboreal primates from this forest, it did correspond well to primate δ18O values.

Cortisol and oxytocin show independent activity during chimpanzee intergroup conflict.

The oxytocinergic system is involved in a range of functions, from attachment and social bonding to aggression and stress responses. Whether oxytocin is released in response to a stressor, shows contradictory results across species and potential contexts-dependent differences. To avoid unintended contextual changes due to experimental procedures, we tested this question non-invasively in wild chimpanzees in an ecologically valid context. We collected endogenous hormonal measures during exposure to a known natural stressor, intergroup conflict. Specifically, we tested for potential synchronous activation patterns between urinary oxytocin and cortisol in male and female chimpanzees during stressor exposure. Oxytocinergic system reactivity during chimpanzee intergroup conflict has already been established in this study population. Thus, we first investigated urinary cortisol levels during border patrol and intergroup encounter days, in comparison to another potential stressor, hunting, and control days. We found higher urinary cortisol levels during intergroup encounter days compared with control and hunting days. We then compared secretion patterns of oxytocin and cortisol in relation to increased levels of out-group contact and hostility ('out-group risk') during intergroup conflict. We found that increased 'out-group risk' was associated with higher cortisol levels, especially when involving direct visual or physical contact with rival groups. Although urinary oxytocin levels were high across intergroup conflict contexts, increasing levels of out-group risk showed no significant variation. Taken together, results indicate independent secretion of oxytocin and cortisol during chimpanzee intergroup conflict, emphasizing that stressor exposure in this context is not the main trigger of oxytocin secretion.

Deletion of Menin in craniofacial osteogenic cells in mice elicits development of mandibular ossifying fibroma.

Ossifying fibroma (OF) is a rare benign tumor of the craniofacial bones that can reach considerable and disfiguring dimensions if left untreated. Although the clinicopathological characteristics of OF are well established, the underlying etiology has remained largely unknown. Our work indicates that Men1-a tumor suppressor gene responsible of Multiple endocrine neoplasia type 1-is critical for OF formation and shows that mice with targeted disruption of Men1 in osteoblasts (Men1Runx2Cre) develop multifocal OF in the mandible with a 100% penetrance. Using lineage-tracing analysis, we demonstrate that loss of Men1 arrests stromal osteoprogenitors in OF at the osterix-positive pre-osteoblastic differentiation stage. Analysis of Men1-lacking stromal spindle cells isolated from OF (OF-derived MSCs (OFMSCs)) revealed a downregulation of the cyclin-dependent kinase (CDK) inhibitor Cdkn1a, consistent with an increased proliferation rate. Intriguingly, the re-expression of Men1 in Men1-deficient OFMSCs restored Cdkn1a expression and abrogated cellular proliferation supporting the tumor-suppressive role of Men1 in OF. Although our work presents the first evidence of Men1 in OF development, it further provides the first genetic mouse model of OF that can be used to better understand the molecular pathogenesis of these benign tumors and to potentially develop novel treatment strategies.

Tools for opening new chapters in the book of Treponema pallidum evolutionary history.

Treponema pallidum infections causing yaws disease and venereal syphilis are globally widespread in human populations, infecting hundreds of thousands and millions annually respectively; endemic syphilis is much less common, and pinta has not been observed in decades. We discuss controversy surrounding the origin, evolution and history of these pathogens in light of available molecular and anthropological evidence. These bacteria (or close relatives) seem to affect many wild African nonhuman primate (NHP) species, though to date only a single NHP Treponema pallidum genome has been published, hindering detection of spillover events and our understanding of potential wildlife reservoirs. Similarly, only ten genomes of Treponema pallidum infecting humans have been published, impeding a full understanding of their diversity and evolutionary history. Research efforts have been hampered by the difficulty of culturing and propagating Treponema pallidum. Here we highlight avenues of research recently opened by the coupling of hybridization capture and next-generation sequencing. We present data generated with such an approach suggesting that asymptomatic bones from NHP occasionally contain enough treponemal DNA to recover large fractions of their genomes. We expect that these methods, which naturally can be applied to modern biopsy samples and ancient human bones, will soon considerably improve our understanding of these enigmatic pathogens and lay rest to old yet unresolved controversies.

The reliability of the diagnostic features in patients with narcolepsy.

This study determined the test-retest reliability of the polysomnographic findings in narcolepsy. The diagnosis of narcolepsy was based on clinical symptoms and polysomnographic signs. Control subjects were screened before participation and were split based on their screening multiple sleep latency test (MSLT) into high- and low-MSLT groups. Subjects completed two polysomnographic evaluations with at least 5 days between laboratory tests. Narcoleptics had lower sleep efficiencies and high stage 1% when compared to the low MSLT control group. They had more awakenings and less stage 2% than the control groups. Narcoleptics had a shorter latency to 1 when compared to the high-MSLT group but comparable to that of the low-MSLT group. Narcoleptics had a higher number of sleep-onset rapid eye movement periods (SOREMPs) than both control groups. The MSLT scores were stable across the two evaluations and showed a statistically significant correlation. Twenty-eight of the 30 narcoleptic subjects had two or more SOREMPs on reevaluation. None of the controls had multiple SOREMPs. Thus, multiple SOREMPs were shown to be a reliable finding in patients with narcolepsy.

HLA DR2 in narcolepsy with sleep-onset REM periods but not cataplexy.

To determine the association of HLA DR2 in patients with narcolepsy without cataplexy, a case-control study was performed. Patients receiving the diagnosis of narcolepsy without cataplexy had excessive daytime sleepiness (EDS) and polysomnographic findings consistent with narcolepsy but no clinical evidence of cataplexy. Of 28 patients identified, 12 agreed to return for HLA typing. Respondents did not differ from nonrespondents in demographic, clinical, or sleep laboratory data. The comparison group was 503 individuals, those 30 years and older, on the Michigan Kidney Transplant Registry. The odds ratio obtained from logistic regression indicated a strong association between narcolepsy without cataplexy and HLA DR2. To control for potential confounding variables, multivariate models were constructed to explore the joint effects of HLA DR2 and each one of the covariates (age, sex, and race), their possible combinations, and the effect of all three covariates. The odds ratios decreased minimally and the association between the disease and HLA DR2 remained significant.

Efficacy of a reduced triazolam dose in elderly insomniacs.

Elderly persons with insomnia are unique because the cause of their insomnia differs from that of younger people and their metabolism of benzodiazepine hypnotics differs as well. This study used nocturnal polysomnography and daytime sleep/wake tendency measures (Multiple Sleep Latency Test, MSLT) to assess the efficacy and safety of a reduced triazolam dosage (0.125 mg) in elderly subjects with insomnia. After 2 nights and an intervening day of screening each subject received triazolam and placebo for 2 consecutive nights presented in a counter-balanced design. Compared to placebo the reduced triazolam dose induced and maintained sleep thereby increasing total sleep time. Sleep stage distribution and the frequency of apneas and periodic leg movements was not altered. The improved sleep was associated with a restoration of the normal pattern of daytime alertness. The correspondence of this clinical data to known pharmacokinetic data is discussed.

Excessive daytime sleepiness associated with insufficient sleep.

Chronic insufficient sleep as an identifiable cause of excessive daytime sleepiness was investigated post hoc by comparing a series of patients with this diagnosis with patients with narcolepsy. Among the prominent features differentiating patients with insufficient sleep from patients with narcolepsy was the report, obtained on the sleep history, of a disparity between the reported amount of sleep obtained on weekdays versus weekends. On evaluation in the laboratory, patients with insufficient sleep showed atypically high sleep efficiency at night and a prolonged sleep time (longer than they report sleeping on a weekday night at home). Compared with patients with narcolepsy, they show a somewhat elevated percentage of stage 3-4 and REM sleep, although this is probably not higher than that of age-matched controls. On the Multiple Sleep Latency Test they displayed moderate sleepiness and no sleep onset REM periods. A mental status examination and Minnesota Multiphasic Personality Inventory did not suggest a primary psychiatric disorder.

Eligibility requirements in hypnotic trials.

Forty-eight patients complaining of insomnia were studied at two sleep laboratories using an identical protocol to evaluate hypnotic efficacy. All met the screening requirement of a mean sleep latency of 30 min or greater on 3 laboratory nights following an adaptation night. Of these patients 34 still complaining of insomnia were screened a second time 2 to 6 months later. Sixteen of the 34 failed the second screen. Sleep parameters for the 34 on screen 1 compared with screen 2 were the same except for sleep latency (the eligibility criteria), which was significantly shorter. There was no evidence of a systematic difference between laboratories, a change in procedure from screen 1 to 2, or a systematic loss of patients from screen 1 to 2. The data show that the statistical phenomenon of regression toward the mean must be considered in designing hypnotic efficacy studies.

Sleep-wake abnormalities in narcolepsy.

To evaluate the degree to which sleep (REM vs. NREM) intrudes into wake and wake intrudes into sleep in narcolepsy, 103 patients with narcolepsy were compared to 105 patients with other diagnoses of disorders of excessive sleep (DOES). Narcoleptic patients had more frequent REM onsets on the multiple sleep latency test (MSLT) and nocturnal polysomnograms. But the MSLT latencies to REM versus NREM in narcoleptic patients did not differ. Nocturnal measures of REM pressure, percentage of REM, and REM latency excluding the REM onsets, did not differ among patient groups. With respect to the intrusion of wake into sleep, narcoleptic patients had more and longer awakenings compared with other DOES patients, but the distribution of wake into REM and NREM sleep did not differ among groups. These data suggest that narcolepsy is not exclusively a REM-related disorder, but involves an inability to sustain a specific neural state for periods comparable to those in normal subjects or other DOES patients.

Alerting effects of naps in patients with narcolepsy.

As part of their standard diagnostic evaluation, 45 patients with narcolepsy and 45 patients with other disorders of excessive sleepiness (DOES), primarily obstructive sleep apnea, each underwent one of three nap conditions that involved manipulating time in bed on the 1600 h latency test of the standard multiple sleep latency test (MSLT) and varying the time between the 1600-h latency test and a subsequent fifth latency test. Compared with the mean of tests 1-4, a 15-min nap at 1600 h (condition 1) increased latency to stage 1 sleep on a latency test 15 min later in both groups. However, the increase was greater for patients with narcolepsy than with other DOES. A 30-min nap at 1600 h (condition 2) produced increased latency 15 min later, but the increase was greater for patients with other DOES. While narcoleptic patients showed no change in latency as a function of increased nap duration, the other DOES patients had increased latencies. When tested 30 min after a 15-min nap (condition 3), narcoleptic patients had latencies that did not differ from those of tests 1-4, while the other DOES patients sustained their increased latencies.

Periodic movements during sleep, sleep fragmentation, and sleep-wake complaints.

To better understand the relation of sleep complaint to sleep continuity and periodic movements during sleep (PMS), two groups of patients were studied retrospectively. One group of 51 patients, 26 men and 25 women, with a mean age of 56.4 years, complained of insomnia. The other group of 29 patients, 20 men and nine women, with a mean age of 55.8 years, complained of excessive daytime sleepiness. Sleepy patients differed significantly from insomnia patients in that they fell asleep faster and slept longer. They showed more frequent arousals (shifts to stage 1 sleep and number of awakenings) than insomnia patients who had longer arousals (mean duration of awakenings). Insomnia patients had more series of PMS, but sleepy patients had more PMS bursts per series.

The effects of doxepin HCl on sleep and depression.

The effects of doxepin hydrochloride (Adapin) on sleep and depression were evaluated in nine depressed patients with documented sleep difficulties. All subjects were screened for depression on the Hamilton Psychiatric Rating Scale. Sleep disturbance was measured by all-night polysomnography. Doxepin in doses of 75 and 150 mg/day significantly improved sleep efficiency, as evidenced by decreased sleep latency and increased total sleep time. After 2 weeks of treatment, REM latency and percent REM time were dramatically changed. Maximal improvement in depression occurred after 2 weeks of doxepin therapy and at the 150 mg dose.

Personality differences between insomniac and non-insomniac psychiatry outpatients.

The relationship between self-reported measures of sleep disturbance and psychopathology was investigated. Previous studies on this topic have failed to use appropriate control groups. The current study examined the relationship between sleep disturbance and personality using insomniac and non-insomniac outpatient counseling clients. The results confirm the significant and positive relation between emotional disturbance and insomnia. The insomniac group showed the expected pattern of MMPI abnormalities (elevated D, Hy, Pt and Sc). However, only the Pt scale of the MMPI and the Cornell Medical Index significantly differentiated the two groups. This suggests that characteristics such as obsessional worry which lead to elevated Pt scores play a more important and unique role in insomnia than previously hypothesized.

Predictors of objective level of daytime sleepiness in patients with sleep-related breathing disorders.

Excessive daytime sleepiness, the most prevalent symptom associated with the OSAS, is hypothesized to result from either fragmentation of sleep or hypoxemia during sleep. Measures of nocturnal sleep, respiration during sleep, and daytime sleepiness in 466 patients with apnea were collected to evaluate these two hypotheses. The various parameters were submitted to correlation and multiple regression analyses to predict daytime sleepiness as measured by the MSLT. The RAI, which measures the number of arousals from sleep associated with respiratory disturbances (best fragmentation correlation), produced a higher correlation with MSLT scores than did TMES (best hypoxemia correlation); however, the measures were highly intercorrelated, and multiple regression analyses to determine which parameters independently predicted MSLT showed the single best predictor to be the RAI. Additional independent variance in MSLT score was explained by TST and PSG1. Measures of hypoxemia provided little or no independent predictive information. These data support the hypothesis that sleep fragmentation is an important determinant of daytime sleepiness in patients with apnea.