Distinct correlations of vasopressin release within the lateral septum and the bed nucleus of the stria terminalis with the display of intermale aggression

Arginine vasopressin (AVP) has been implicated in a wide variety of social behaviors ranging from affiliation to aggression. However, the precise functional involvement of AVP in intermale aggression is still a matter of debate. In fact, very little is known about AVP release patterns within distinct brain regions during the display of intermale aggression and, in turn, the behavioral consequences of such release. We used intracerebral microdialysis to monitor local AVP release within the lateral septum (LS) and the bed nucleus of the stria terminalis (BST) of adult male Wistar rats during the resident-intruder (RI) test. Resident males were cohabitated with a female prior to the RI test to stimulate intermale aggression toward the intruder male. AVP release within the LS correlated positively with intermale aggression. The specific AVP V1a receptor antagonist d(CH₂)₅Tyr(Me)AVP (10 μg/ml) administered via retrodialysis (3.3 µl/min, 30 min) into the LS of high-aggressive rats prior to the second RI test, prevented an increase in aggression in the second compared with the first RI test as seen in vehicle-treated high-aggressive rats. In contrast to the LS, AVP release within the BST correlated negatively with intermale aggression. Moreover, retrodialysis of synthetic AVP (1 µg/ml) administered into the BST of high-aggressive rats significantly reduced the display of aggression during the second RI test. These data reveal that AVP can both promote and inhibit intermale aggression, depending upon the brain region in which AVP is released. Although challenging the general view that central AVP release enhances intermale aggression in rodents, our data support a model in which AVP coordinates a range of social behaviors by eliciting region-specific effects.     

Short-term exposure to testosterone propionate leads to rapid bill color and dominance changes in zebra finches

Testosterone (T) can influence both male-male competition and mate choice displays. In zebra finches, female mate choice is based in part on bill color, and bill color has been shown to be enhanced by long-term testosterone supplementation. However, it is not clear whether bill color plays a role in male-male interactions and how bill color responds to shorter-term changes in T. We tested whether a single injection of testosterone propionate (TP) would influence male-male dominance interactions and lead to rapid (over a three-day period) changes in bill color. In addition, we tested whether bill color predicted aggression and dominance. We allowed birds in triads to establish hierarchies and then injected either dominant or subordinate individuals with TP, in addition to establishing sham control triads. We found that red chroma, but not hue, predicted aggressiveness of males. Exposure to TP led both dominant and subordinate birds to increase dominance scores over three days, longer than the < 24 h period in which injected TP stays active. In addition, exposure to TP increased red chroma and hue in three days showing the dynamic nature of allocation of pigments to the bill. Our results suggest that zebra finches can modulate T and bill color levels over short time periods and these changes may occur through positive feedback between T-levels and dominance.     

Intergroup encounters in wild white-faced capuchins (Cebus capucinus)

Wrangham (1980) hypothesized that knowledge of the nature of intergroup encounters is crucial to understanding primate social relationships and social organization. I studied a single social group of wild white-faced capuchins over a period of 26 months and observed 44 encounters between social groups during 3703 hr of observation. All intergroup encounters consisted of predominantly hostile social interactions. However, nonaggressive interactions between males of different social groups occurred in a few cases. Adult males were the sole participants in 39 encounters and the primary participants in all 44 encounters. The alpha male was the most frequent participant. High-ranking females participated aggressively in five encounters, and low-ranking females never participated. There was no stable intergroup dominance hierarchy. I hypothesize that the need for male-male cooperation in intergroup aggression is an important factor influencing the quality of intragroup male-male relationships. Behavior during intergroup encounters is consistent with the idea that intergroup behavior is related to male reproductive strategies, but inconsistent with the idea that intergroup aggression is related to female defense of resources. The possibility that males are “hired guns” (Wrangham, 1980) cannot be ruled out.     

Social Relationships among Males in Multimale Siamang Groups

I quantified social and spatial interactions among adults in 4 multimale siamang (Symphalangus syndactylus) groups to evaluate the importance of aggression and avoidance in mediating male-male relationships. Actual genetic relationships among adults are unknown, but available mitochondrial data suggest that in 3 of 4 groups, neither male was the offspring or maternal sibling of the female, whereas in the fourth group, a matrilineal relationship between the female and 1 adult male was not excluded. Rates of aggression involving male-male dyads were very low. One male-female dyad maintained closer spatial cohesion than those of other adult dyads in 3 of 4 groups. Nonetheless, all adult males spent substantial percentages of their time ≤20 m from other adults in their groups. The percentages of time that male-male dyads spent in social grooming interactions did not differ from those of male-female dyads. In 3 groups, both males copulated with the group female. While previous studies have reported high rates of aggression between adult males and subadult male group members in siamangs, my results suggest that male-male relationships in multimale groups at Way Canguk were relatively harmonious. Acceptance of multimale grouping (and in some cases sexual polyandry) suggests that the benefits outweigh the costs under some circumstances. If there was a genetic relationship between males, then tolerance of delayed dispersal and copulation with the adult female may function as a form of parental investment. Males may also benefit from multimale grouping via enhanced territorial defense or reduced costs of mate defense.     

Effects of copulation temperature on female reproductive output and longevity in the wolf spider Pardosa astrigera (Araneae: Lycosidae)

The copulation duration of male wolf spider Pardosa astrigera, was significantly influenced by environmental temperature, as had been found in some insect species. Therefore, temperature during male courtship and copulation may influence the amount of sperm and seminal fluids transferred during copulation, which in turn could influence female fitness. In order to test this hypothesis, we subjected pairs of male and female P. astrigera to five temperature groups from 16 to 32 °C at an interval of 4 °C, and investigated whether and to what extent the various temperatures during male courtship and copulation influenced female reproductive output and female adult longevity under controlled laboratory conditions. With the increase of copulation temperature, females were more likely to lay egg sacs. The total egg sacs and lifetime fecundity of female were positively influenced by copulation temperature, whereas female lifetime spiderlings and adult longevity were independent of copulation temperature.     

Brain-gut interactions between central vagal activation and abdominal surgery to influence gastric myenteric ganglia Fos expression in rats

We previously showed that medullary thyrotropin-releasing hormone (TRH) or the stable TRH agonist, RX-77368 administered intracisternally induces vagal-dependent activation of gastric myenteric neurons and prevents post surgery-induced delayed gastric emptying in rats. We investigated whether abdominal surgery alters intracisternal (ic) RX-77368 (50 ng)-induced gastric myenteric neuron activation. Under 10 min enflurane anesthesia, rats underwent an ic injection of saline or RX-77368 followed by a laparotomy and a 1-min cecal palpation, or no surgery and were euthanized 90 min later. Longitudinal muscle/myenteric plexus whole-mount preparations of gastric corpus and antrum were processed for immunohistochemical detection of Fos alone or double labeled with protein gene-product 9.5 (PGP 9.5) and vesicular acetylcholine transporter (VAChT). In the non surgery groups, ic RX-77368 induced a 17 fold increase in Fos-expression in both gastric antrum and corpus myenteric neurons compared to saline injected rats. PGP 9.5 ascertained the neuronal identity of myenteric cells expressing Fos. In the abdominal surgery groups, ic RX-77368 induced a significant increase in Fos-expression in both the corpus and antrum myenteric ganglia compared with ic saline injected rats which has no Fos in the gastric myenteric ganglia. However, the response was reduced by 73-78% compared with that induced by ic RX 77368 without surgery. Abundant VAChT positive nerve fibers were present around Fos positive neurons. These results indicate a bidirectional interaction between central vagal stimulation of gastric myenteric neurons and abdominal surgery. The modulation of gastric vagus-myenteric neuron activity could play an important role in the recovery phase of postoperative gastric ileus.     

Non-canonical binding of an antibody resembling a naïve B cell receptor immunoglobulin to hepatitis B virus capsids

The hepatitis B virus capsid (core antigen) is able to bind to and activate naïve B cells and these become efficient primary antigen-presenting cells for the priming of T cells. We have investigated this interaction by using cryo-electron microscopy, three-dimensional image reconstruction, and molecular modeling to visualize capsids decorated with Fab fragments of a receptor immunoglobulin, and surface plasmon resonance to measure the binding affinity. By both criteria, the mode of binding differs from those of the six monoclonal anti-core antigen antibodies previously characterized. The Fab interacts with two sites ∼30 Å apart. One interaction is canonical, whereby the CDR loops engage the tip of one of the 25 Å spikes that protrude from the capsid surface. The second interaction is non-canonical; in it, the Fab framework contacts the tip of an adjacent spike. The binding affinity of this Fab for capsids, K_D ∼ 4 × 10^− 7 M, is relatively low for an antibody-antigen interaction, but is ∼ 150-fold lower still (∼ 2.5 × 10^− 5 M) for unassembled capsid protein dimers. The latter observation indicates that both of the observed interactions are required to achieve stable binding of capsids by this receptor immunoglobulin. Considerations of conserved sequence motifs in other such molecules suggest that other naïve B cells may interact with HBV capsids in much the same way.     

Male-male Interactions in Heterosexual and All-male Wild Mountain Gorilla Groups

Variation in male dispersal and behavior patterns are components of intraspecific differences in social systems. A comparison of male behavior in different social settings can be useful for determining which behavioral mechanisms contribute to variability in social systems. Two heterosexual multimale groups and one all-male group of mountain gorillas (Gorilla gorilla beringei) were observed for over 1100 h at the Karisoke Research Centre, Rwanda. Data on proximity patterns, dominance relationships, aggression, agonistic interventions, affiliation, and homosexual behavior were compared among the males in these groups to examine the influence of female presence, sex ratio, group size, and kinship on male—male interactions. Males in the all-male group stayed closer together, affiliated more, exhibited more homosexual behavior, and were more aggressive toward each other than males in heterosexual groups. However, the males in heterosexual groups showed more wounding and more consistent dominance relationships. Kinship did not influence male-male relationships in the all-male group. The males in the heterosexual groups rarely interacted with one another; they may actively avoid close proximity to reduce aggression. Results suggest that the variable social system of mountain gorillas may be more strongly influenced by demographic factors, male-female social relationships, and male-male competition for mates than by any benefits of male-male relationships.     

Sperm competition within a dominance hierarchy: investment in social status vs. investment in ejaculates

There is increasing recognition that male-male competition can take many forms, but as yet the form is not predictable a priori. Many recent studies have focused attention on how males in disadvantaged mating roles compensate through sperm competition. However, mating systems in which subordinate males are reproductively suppressed, particularly through the stress of social interactions, may limit the ability of males to respond by increasing investment in sperm quality. We examined the interaction between social status and ejaculate tactics in Nauphoeta cinerea, a cockroach that has a mating system with well-characterized dominance hierarchies. Both social experience with other males and social status influenced aspects of ejaculates. The stress of social interactions reduced the size of the ejaculate and number of sperm inseminated. In ejaculates formed prior to social experience, however, males that go on to become dominant inseminated more sperm than males that go on to become subordinate, suggesting innate differences among males. Our results show that though selection for increased success in sperm competition for subordinate males in a hierarchy can occur, both the traits and the way in which the balance between pre- and post-copulatory strategies is negotiated will depend on specific details of the mating system. These details will include how the physiological effects of social interactions may limit selection through male-male competition.     

Structure and antioxidant activity of an extracellular polysaccharide from coral-associated fungus, Aspergillus versicolor LCJ-5-4

An extracellular polysaccharide AVP was isolated from the fermented broth of coral-associated fungus Aspergillus versicolor LCJ-5-4. AVP was a mannoglucan with molecular weight of about 7 kDa, and the molar ratio of glucose and mannose was 1.7:1.0. On the basis of detailed one- and two-dimensional nuclear magnetic resonance (1D and 2D NMR) spectroscopic analyses, the backbone of AVP was characterized to be composed of (1 → 6)-linked α-d-glucopyranose and (1 → 2)-linked α-d-mannopyranose units. The mannopyranose residues in the backbone were substituted mainly at C-6 by the side chain of (1 → 2)-linked α-d-mannopyranose trisaccharides units. The antioxidant activity of AVP was evaluated with the scavenging abilities on 1,1-diphenyl-2-picrylhydrazyl (DPPH), superoxide and hydroxyl radicals in vitro, and the results indicated that AVP had good antioxidant activity, especially scavenging ability on superoxide radicals. AVP was a novel extracellular polysaccharide with different structural characteristics from other extracellular polysaccharides and could be a potential source of antioxidant.     

Circulating obestatin is increased in patients with cardiorenal syndrome and positively correlated with vasopressin

Obestatin regulates fluid and electrolyte homeostasis mainly by opposing the action of vasopressin (AVP). We measured plasma concentration of obestatin and AVP in patients with cardiorenal syndrome (CRS). Plasma AVP and obestatin concentration were measured in 34 patients with type II CRS. The data were compared to that in 31 patients with chronic kidney disease (CKD), 41 patients with chronic heart failure (CHF) and 30 healthy subjects. Obestatin was significantly higher in the patients with CRS (355.8 ± 85.1 pg/ml) than that in the healthy controls (212.3 ± 37.9 pg/ml, P < 0.01), the patients with CKD (246.7 ± 34.3 pg/ml, P < 0.01) and the patients with CHF (258.4 ± 112.1 pg/ml, P < 0.01). AVP was also significantly higher in the patients with CRS (65.1 ± 36.0 pg/ml) than that in the healthy controls (38.5 ± 20.1 pg/ml, P < 0.01), the patients with CKD (50.4 ± 24.8 pg/ml, P < 0.01) and the patients with CHF (54.6 ± 16.3 pg/ml, P < 0.01). Plasma concentration of obestatin was positively correlated with AVP plasma concentration in the overall analysis that included subjects from all disease categories (r = 0.219, P < 0.05), but not within the CRS group. Plasma obestatin and vasopressin were elevated in patients with CRS. Plasma obestatin concentration seemed to be positively correlated with plasma AVP.     

Male Mating Success in the Presence of a Conspecific Opponent in a Madagascar Hissing Cockroach,Gromphadorhina portentosa (Dictyoptera: Blaberidae)

The influence of a conspecific competitor on male mating behavior was examined in a Madagascar hissing cockroach, Gromphadorhina portentosa. Previous studies have suggested that both male-male competition and female discrimination during courtship interactions may influence male mating success. Familiar pairs of males with a known social association were placed in an arena with a single virgin female and observed. As expected, subordinate males mated significantly less often than their dominant opponents. In pairs in which one male mated, dominant individuals limited the access of subordinates to females. Dominant males displayed an increased frequency and duration of interaction with the female. However, in pairs where both males remained unmated, the mating behavior of dominant and subordinate males did not differ significantly. As interactions progressed, as in the case of males that remained unmated, subordinate males gained increased access to the female. Mated males tended to be larger than their opponent although within a rank, males that mated were no larger than those that remained unmated. These results are discussed in light of the possible roles of male-male competition and female discrimination during courtship interactions.     

C-reactive protein induces G2/M phase cell cycle arrest and apoptosis in monocytes through the upregulation of B-cell translocation gene 2 expression

We hypothesized that C-reactive protein (CRP) may affect the cell cycle and induce apoptotic changes of monocytes. CRP (∼25 μg/ml) significantly increased expressions of B-cell translocation gene 2 (BTG2) mRNA and protein in human monocytes through pathways involving CD32/NADPH oxidase 2/p53, which eventually induced G2/M phase arrest and apoptotic cell death. Such pro-apoptotic effect of CRP was not found in thioglycollate-elicited intraperitoneal monocytes/macrophages harvested from BTG2-knockout male C57BL/6 mice (n = 5). Within atheromatous plaques obtained from CRP-transgenic male LDLR^−/− C57BL/6 mice (n = 5) and human coronary arteries, BTG2 co-localized with CRP, p53 and monocytes/macrophages. Therefore the pro-apoptotic pathway of CRP-CD32-Nox2-p53-BTG2 may contribute to the retardation of the atherogenic process.     

Apolipoprotein A-V associates with intrahepatic lipid droplets and influences triglyceride accumulation

Apolipoprotein A-V (apoA-V), secreted solely by the liver, is a low abundance protein that strongly influences plasma triglyceride (TG) levels. In vitro, in transfected hepatoma cell lines apoA-V is largely retained within the cell in association with cytosolic lipid droplets (LD). To evaluate if this is true in vivo, in the present study the amount of apoA-V in the plasma compartment versus liver tissue was determined in APOA5 transgenic (Tg) mice. The majority of total apoA-V (∼ 80%) was in the plasma compartment. Injection of APOA5 Tg mice with heparin increased plasma apoA-V protein levels by ∼ 25% indicating the existence of a heparin-releasable pool. Intrahepatic apoA-V was associated with LD isolated from livers of wild type (WT) and APOA5 Tg mice. Furthermore, livers from APOA5 Tg mice contained significantly higher amounts of TG than livers from WT or apoa5 knockout mice suggesting that apoA-V influences intrahepatic TG levels.     

Postconflict Affiliation Between Former Opponents in Macaca thibetana on Mt. Huangshan, China

We describe basic patterns of postconflict affiliation between former opponents within a group of wild, provisioned Tibetan macaques Macaca thibetana on Mt. Huangshan, China. Like most primates studied to date, Tibetan macaques reconciled, i.e., overall they engaged in affiliative interaction with opponents at higher rates immediately after an aggressive conflict than at other times. Probabilities of affiliation were enhanced ≤30 s after the end of hostilities. However when we examined sex partner combinations separately, we found unequivocal evidence for reconciliation only for male-male dyads. Tolerant interaction among other partner combinations apparently was not disrupted after a conflict, presumably obviating the need to reconcile. One aspect of reconciliation among males was consistent with other indications of a despotic dominance style: aggressors initiated a higher proportion of affiliative interactions after a conflict than at other times. Another aspect of reconciliation was more typical of relaxed dominance styles: males used specialized behaviors (embraces and same-sex mounts) disproportionately to reconcile. We also found inconsistent evidence for the valuable relationship hypothesis; probabilities of reconciliation were enhanced for male-male dyads with the closest affiliative relationships, but not for those that displayed the most tolerance or mutual agonistic support. We discuss reconciliation and other aspects of conflict management among males in the context of a group with nearly even sex ratios and high male-male mating competition.     

Changes in sperm quality and numbers in response to experimental manipulation of male social status and female attractiveness

In promiscuous species, male reproductive success is determined by the interaction between the ability to access and choose females of the highest reproductive quality and, after copulation, the ability to outcompete the ejaculates of rival males. Disentangling the factors regulating the interplay between traits conferring a reproductive advantage before and after copulation is therefore crucial to understanding how sexual strategies evolve. Here we show in the fowl Gallus gallus, where social status determines copulation success, that dominant males produce more sperm than subordinates but that the quality of dominant males' sperm decreases over successive copulations, whereas that of subordinates remains constant. Experimentally manipulating male social status confirmed that ejaculate quality (the number and quality of sperm produced) was a response to the social environment rather than the result of intrinsic differences between dominant and subordinate males. We further show that dominant males responded to variation in female sexual ornamentation, which signals reproductive quality, by adjusting the number and quality of sperm they transferred, whereas subordinate males did not: they transferred ejaculates of similar quality to females with different ornament sizes. These results indicate that trade-offs between traits influencing reproductive success before and after copulation, combined with variation in social dynamics and female quality, may favor the evolution of phenotypically plastic alternative reproductive strategies.     

Involvement of different mesotocin (oxytocin homologue) populations in sexual and aggressive behaviours of the brown anole

The oxytocin (OT) family of neuropeptides are known to modulate social behaviours and anxiety in mammals and birds. We investigated cell numbers and neural activity, assessed as Fos induction, within magnocellular and parvocellular populations of neurons producing the OT homologue mesotocin (MT, Ile⁸-oxytocin). This was conducted within the male brown anole lizard, Anolis sagrei, following agonistic or courtship encounters with a conspecific. Both neurons colocalizing and not colocalizing corticotropin-releasing factor (CRF) were examined. Parvocellular neurons of the paraventricular nucleus exhibited a positive correlation between courtship frequency and Fos colocalization, regardless of whether they produce just MT or MT + CRF. Magnocellular populations showed only trends towards positive relationships with courtship and no cell populations showed aggression-related Fos induction. These findings are novel because they demonstrate the involvement of MT neurons in male social behaviour, especially in reptiles for whom the involvement of MT in social behaviour was previously unknown.     

Role of exchange and dipolar interactions in the radical pair model of the avian magnetic compass

It is not yet understood how migratory birds sense the Earth's magnetic field as a source of compass information. One suggestion is that the magnetoreceptor involves a photochemical reaction whose product yields are sensitive to external magnetic fields. Specifically, a flavin-tryptophan radical pair is supposedly formed by photoinduced sequential electron transfer along a chain of three tryptophan residues in a cryptochrome flavoprotein immobilized in the retina. The electron Zeeman interaction with the Earth's magnetic field (∼50 μT), modulated by anisotropic magnetic interactions within the radicals, causes the product yields to depend on the orientation of the receptor. According to well-established theory, the radicals would need to be separated by >3.5 nm in order that interradical spin-spin interactions are weak enough to permit a ∼50 μT field to have a significant effect. Using quantum mechanical simulations, it is shown here that substantial changes in product yields can nevertheless be expected at the much smaller separation of 2.0 ± 0.2 nm where the effects of exchange and dipolar interactions partially cancel. The terminal flavin-tryptophan radical pair in cryptochrome has a separation of ∼1.9 nm and is thus ideally placed to act as a magnetoreceptor for the compass mechanism.     

Agonistic behavior and electrical stimulation of the antennae induces Fos‐like protein expression in the male cricket brain

Immediate early genes (IEG) such as c‐Fos and Fos‐related antigens (FRA) have been used as markers of neuronal activation. In this study, we determined whether the expression of c‐Fos/FRAs is increased in the brains of adult male Acheta domesticus crickets following agonistic interactions. We looked for c‐Fos/FRA proteins in the brain of un‐fought, control male crickets and of dominant and subordinate male crickets sacrificed at different time periods following an agonistic interaction. Using immunoblot analysis, we found four different c‐Fos/FRA‐like proteins in the adult cricket brain. Continuous agonistic interaction increased c‐Fos/FRA protein expression in the brains of subordinate males compared to control and dominant males. In addition, direct electrical stimulation of the male cricket antennae increased c‐Fos/FRA‐like protein in the brain. We identified the specific brain regions that exhibit c‐Fos/FRA‐like immunoreactivity in crickets. We detected c‐Fos/FRA‐like cellular immunoreactivity in different functional regions of the adult brain including the pars intercerebralis, protocerebrum, deutocerebrum, and the cortex of the mushroom bodies. © 2010 Wiley Periodicals, Inc.