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PubMed2004

Mast cells--a role in periodontal diseases?

OBJECTIVES: Limited attention has been given to the role mast cells may play in periodontal diseases. BACKGROUND: Mast cells are indeed found abundantly below and within several types of mucosal epithelia. On the basis of their proteinase content, mast cells are divided into connective tissue (CT) and mucosal phenotypes. The CT phenotype contains both tryptase and chymase (MC(TC)), while the mucosal phenotype contains only tryptase (MC(T)). The in vivo significance of different mast cell phenotypes has not yet been fully established. Mast cells are able to phagocytose, process and present antigens as effectively as macrophages. RESULTS: Recently mast cells were found in high numbers in chronically inflamed gingival tissue taken from patients with chronic marginal periodontitis (CMP). The number of mast cells was found to be even higher in HIV(+) patients with CMP. Furthermore, mast cells also express strongly matrix metalloproteinases (MMPs), which are key enzymes in degradation of gingival extracellular matrix. Mast cells may release preformed cytokines directing local innate and adaptive immune responses. The present review will focus on possible roles for mast cells in periodontal diseases. CONCLUSIONS: We certainly feel that this is a key cell in inflamed periodontal tissue and its role in periodontitis needs to be revisited.

Cytokines↗
PubMed2002

The evolving transmission pattern of Rift Valley fever in the Arabian Peninsula.

Vector-borne viruses are no respecters of international boundaries. The recent outbreak of Rift Valley fever (RVF) in the Kingdom of Saudi Arabia (KSA) and Yemen in September 2000 clearly sends a message that once pathogens cross their known geographic limits, they tend to adapt to the local ecology in order to survive and maintain transmission. This paper examines the various factors that may contribute to the establishment of RVF in the Arabian Peninsula (AP) and its possible spread to other countries. The annual influx of over 2 million pilgrims for the Hajj (annual pilgrimage for Muslims) in the KSA, as well as the large migrant population in this region, generates high human and animal traffic that presents a challenging agenda for public health. The potential risks within this period as well as other peculiar ecological factors are discussed.

Animals↗
PubMed1977

Sodium chloride transport across the chicken coprodeum. Basic characteristics and dependence on sodium chloride intake.

1. The transport characteristics of the chicken coprodeum have been examined in vitro using the isolated mucosa. The short-circuit current (I(sc)), the transepithelial electrical potential difference (p.d.), the unidirectional transmural fluxes (J(ms), J(sm)) of sodium and chloride measured in the short-circuited state, and the unidirectional influx of sodium and chloride across the brush border membrane measured under open-circuit conditions have been studied. The effect of the sodium chloride contents of the diet on these parameters have been investigated.2. The isolated mucosa depends functionally on the presence of glucose in the incubation media. This dependence reflects the need of glucose as a fuel. There is no indication of coupling between transport of sugars and sodium across the brush border membrane. For preparations from chickens on a low sodium diet a very high and stable I(sc) can quantitatively be accounted for by the net transport of sodium. Influx of sodium across the brush border membrane is not significantly different from the net flux of sodium. By feeding the chickens a high sodium diet the I(sc) is reduced by more than 95%, the net transport of sodium is abolished, and the transepithelial electrical conductance is reduced by more than 50%.3. Both unidirectional transepithelial fluxes of chloride, and the serosa to mucosa flux of sodium appear to proceed through a paracellular shunt.4. Under the conditions of the low sodium diet the paracellular pathway appears to be anion selective. Whereas, under the conditions of the high sodium regimen the paracellular route appears to be cation selective. After adaptation to a high sodium diet the influx of sodium across the brush border membrane is only moderately reduced. Consequently the decisive event in the adaptation must be localized elsewhere.

Animals↗
PubMed2002

The focal adhesion protein paxillin regulates contraction in canine tracheal smooth muscle.

The adapter protein paxillin localizes to the focal adhesions of adherent cells and has been implicated in the regulation of cytoskeletal organization and cell motility. Paxillin undergoes tyrosine phosphorylation in response to the contractile stimulation of tracheal smooth muscle. We therefore hypothesized that paxillin may be involved in regulating smooth muscle contraction. Tracheal smooth muscle strips were treated with paxillin antisense oligonucleotides to inhibit the expression of paxillin protein selectively. Paxillin antisense or sense was introduced into muscle strips by reversible permeabilization and strips were incubated with antisense or sense for 3 days. Paxillin antisense selectively depressed paxillin expression, but it did not affect the expression of vinculin, focal adhesion kinase, myosin light chain kinase, myosin heavy chain or myosin light chain. Tension development in response to stimulation with ACh or KCl was markedly depressed in paxillin-depleted muscle strips. Active force and paxillin protein expression were restored by incubation of antisense-treated strips in the absence of oligonucleotides. The depletion of paxillin did not inhibit the increase in intracellular free Ca2+, myosin light chain phosphorylation or myosin ATPase activity in response to contractile stimulation. The concentration of G-actin was significantly lower in unstimulated paxillin-depleted smooth muscle tissues than in normal tissues. While stimulation with acetylcholine caused a decrease in G-actin in normal muscle strips, it caused little change in the G-actin concentration in paxillin-depleted muscle strips, suggesting that paxillin is necessary for normal actin dynamics in smooth muscle. We conclude that paxillin is required for active tension development in smooth muscle, but that it does not regulate increases in intracellular Ca2+, myosin light chain phosphorylation or myosin ATPase activity during contractile stimulation. Paxillin may be important in regulating actin filament dynamics and organization during smooth muscle contraction.

Acetylcholine↗
PubMedDate not supplied

Missing tissue compensators: evaluation and optimization of a commercial system.

A commercial system for producing retracted compensators has been adapted to suit local needs, and is evaluated here. It comprises a magnetic field surface digitizer and computer-driven milling machine. Improvements in dose distributions, resulting in standard deviations of the mean dose between 2% and 3%, have been achieved for treatment fields in wax phantoms simulating the head and neck regions. Optimization of compensator shape to allow for changes in the amount of scattered radiation has resulted in a further improvement in dose uniformity, particularly near the field borders; for these compensators the standard deviation was as low as 1.6%. The system using the basic algorithm has been in clinical use since July.

Humans↗
PubMed2002

Genotypic and phenotypic diversity within species of purple nonsulfur bacteria isolated from aquatic sediments.

To assess the extent of genotypic and phenotypic diversity within species of purple nonsulfur bacteria found in aquatic sediments, a total of 128 strains were directly isolated from agar plates that had been inoculated with sediment samples from Haren and De Biesbosch in The Netherlands. All isolates were initially characterized by BOX-PCR genomic DNA fingerprinting, and 60 distinct genotypes were identified. Analyses of 16S rRNA gene sequences of representatives of each genotype showed that five and eight different phylotypes of purple nonsulfur bacteria were obtained from the Haren and De Biesbosch sites, respectively. At the Haren site, 80.5% of the clones were Rhodopseudomonas palustris, whereas Rhodoferax fermentans and Rhodopseudomonas palustris were numerically dominant at the De Biesbosch site and constituted 45.9 and 34.4% of the isolates obtained, respectively. BOX-PCR genomic fingerprints showed that there was a high level of genotypic diversity within each of these species. The genomic fingerprints of Rhodopseudomonas palustris isolates were significantly different for isolates from the two sampling sites, suggesting that certain strains may be endemic to each sampling site. Not all Rhodopseudomonas palustris isolates could degrade benzoate, a feature that has previously been thought to be characteristic of the species. There were differences in the BOX-PCR genomic fingerprints and restriction fragment length polymorphisms of benzoate-coenzyme A ligase genes and form I and form II ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO) genes between benzoate-degrading and non-benzoate-degrading genotypes. The ability to distinguish these two Rhodopseudomonas palustris groups based on multiple genetic differences may reflect an incipient speciation event resulting from adaptive evolution to local environmental conditions.

Benzoates↗
PubMed1992

Immunocytological responses in porcine proliferative enteropathies.

The ileum, colon, and mesenteric lymph nodes of pigs naturally affected by either of the two major forms of proliferative enteropathy, namely, intestinal adenomatosis or hemorrhagic enteropathy, were examined for immunocytological responses to infection by immunocytochemistry, using antibodies directed against elements of the porcine immune system. In both forms, there was mucosal proliferation of immature enterocytes which lacked substantial major histocompatibility complex class II expression and a marked accumulation of immunoglobulin A (IgA) at the apical cytoplasm of affected enterocytes in association with intracellular Campylobacter-like organisms. In intestinal adenomatosis, there was only a mild infiltration of CD8+ and CD25+ T cells in the intestinal lamina propria. In hemorrhagic enteropathy, there was a moderate infiltration of CD8+ and CD25+ T cells and IgM+ B cells in the lamina propria. In rats and humans, villous enterocytes are thought to act as antigen-presenting cells, with major histocompatibility complex class II molecules present on their surface, capable of initiating a T-cell response (particularly of CD8+ T cells) in response to bacterial antigens. Therefore, the selection of immature crypt cells by the intracellular Campylobacter-like organisms for entry and multiplication may represent a remarkable microbial adaptation associated with local immunomodulation and enhanced bacterial survival. The accumulation of IgA within affected enterocytes may represent a reduced capability of the cells to process nonspecific IgA or an accumulation of specific IgA.

Animals↗
PubMed2002

Development and evaluation of a DNA enzyme immunoassay method for env genotyping of subtypes A through G of human immunodeficiency virus type 1 group M, with discrimination of the circulating recombinant forms CRF01_AE and CRF02_AG.

The tools currently available for genetic subtyping of human immunodeficiency virus type 1 are laborious or can be used only for the analysis of a limited number of samples and/or subtypes. We developed and evaluated a molecular biology-based method using subtype-specific oligonucleotide probes for env genotyping of subtypes A through G, CRF01_AE, and CRF02_AG. DNA enzyme immunoassay (DEIA) genotyping is based on nested PCR amplification of the 5' end of the env gene (proviral DNA), followed by subtype-specific hybridization and immunoenzymatic detection on microplates. DEIA genotyping was validated with a large number of samples (n = 128) collected in Europe (France; n = 47), West-Central Africa (Cameroon; n = 36), and West Africa (Senegal; n = 45). Three different formats, depending on the distribution of subtypes in the three countries, were developed. The results were compared with those obtained by sequencing of the V3-V5 region and phylogenetic analysis or an env heteroduplex mobility assay. Additional sequencing and phylogenetic analyses of the DEIA region (the first codon of the env coding sequence to the middle of conserved region C1 of gp120) were performed to investigate the reasons for discrepancies. Intense and highly specific reactions between the oligonucleotide probes and the corresponding samples were observed. Overall, correct identification was achieved for 107 of 128 samples (83.6%). One sample was not amplified, 10 (8%) were nontypeable (NT), and 10 (8%) were misidentified. Six of the 10 discordant samples were further investigated by phylogenetic analysis, which indicated that these samples corresponded to recombinants involving the env 5' end and the V3 and V5 regions of the two parental clades. Sequencing of NT samples showed numerous differences between sample and probe sequences, resulting in a lack of hybridization, and revealed the limitations of the selected probes in terms of specificity and sensitivity. We demonstrated the feasibility of DEIA genotyping: six subtypes plus the two most prevalent circulating recombinant forms were discriminated by using the 5' end of the env gene. This method can be adapted to the local situation by including only probes that correspond to the prevalent strains.

DNA, Viral↗
PubMed2004

Effect of interaction between hepatitis C virus NS5A and NS5B on hepatitis C virus RNA replication with the hepatitis C virus replicon.

Hepatitis C virus (HCV) NS5A has been reported to be important for the establishment of replication by adaptive mutations or localization, although its role in viral replication remains unclear. It was previously reported that NS5A interacts with NS5B via two regions of NS5A in the isolate JK-1 and modulates the activity of NS5B RdRp (Y. Shirota et al., J. Biol. Chem., 277:11149-11155, 2002), but the biological significance of this interaction has not been determined. In this study, we addressed the effect of this interaction on HCV RNA replication with an HCV replicon system derived from the isolate M1LE (H. Kishine et al., Biochem. Biophys. Res. Commun., 293:993-999, 2002). We constructed three internal deletion mutants, M1LE/5Adel-1 and M1LE/5Adel-2, each encoding NS5A which cannot bind NS5B, and M1LE/5Adel-3, encoding NS5A that can bind NS5B. After transfection into Huh-7 cells, M1LE/5Adel-3 was replication competent, but both M1LE/5Adel-1 and M1LE/5Adel-2 were not. Next we prepared 20 alanine-substituted clustered mutants within both NS5B-binding regions and examined the effect of these mutants on HCV RNA replication. Only 5 of the 20 mutants were replication competent. Subsequently, we introduced a point mutation, S225P, a deletion of S229, or S232I into NS5A and prepared cured Huh-7 cells that were cured of RNA replication by alpha interferon. Finally, with these point mutations and cured cells, we established a highly improved replicon system. In this system, only the same five mutants were replication competent. These results strongly suggest that the interaction between NS5A and NS5B is critical for HCV RNA replication in the HCV replicon system.

Amino Acid Sequence↗
PubMed1998

Socioeconomic barriers to cataract surgery in Nepal: the South Asian cataract management study.

BACKGROUND: Previous studies have shown that, despite an increasing availability of cataract surgery, important socioeconomic barriers exist in the acceptance of surgery in many rural areas of south Asia. Nepal has developed a comprehensive national network of eye hospitals but the surgical coverage for the treatment of cataract blind is still low. AIMS: To determine the utilisation of cataract surgery and the level of physical and psychosocial impairment and the socioeconomic barriers to surgery in a group of non-acceptors of surgery. METHODS: Of 319 cataract patients identified in a field screening 96 non-acceptors of surgery were interviewed 1 year after an offer to undergo surgery. The interview included questions on visual function, quality of life, and socioeconomic variables on acceptance of cataract surgery. The quality of life questionnaire was based on the field validated protocol addressing the impact of visual impairment on physical and psychosocial functions. The questionnaire was adapted to the local conditions after pretesting. Data were analysed by degree of visual impairment. RESULTS: Of 319 cataract patients identified only 45.5% accepted surgery, with men accepting surgery more readily than women (RR = 1.31; 95% CI = 1.04-1.67) because of a significantly greater acceptance of surgery in men in the non-blind group. The acceptance rate was significantly higher in the blind group (RR = 1.74; 95% CI = 1.36-2.22) compared with those patients having impairment of vision and severe loss of vision. Of 96 non-acceptors interviewed only a further 13% accepted surgery after a second counselling. The most frequent reasons given for not accepting surgery were economic (48%) and logistical (44.8%) constraints followed by fear of surgery (33.3%) and lack of time (18.8%). Half of the subjects complained of problems with self care but only 10% needed help for their most basic every day activities. 17.7% said they needed help to visit neighbours and 26% needed help to attend the field or market. CONCLUSIONS: It was found that in this population with a majority of patients with severe vision loss and blind, even when offered transport and free surgery the utilisation of cataract surgery is below 60%. Medicine tends to be prescriptive based on technological advances that it is able to offer. Medical practice needs to develop a more holistic understanding of the needs of the communities cultivating a greater capability to analyse the role of cultural, social, and economic factors when planning medical services for the population.

Activities of Daily Living↗
PubMed2003

Mobile polymer connectors.

We study the junction between two solid objects, formed by polymer connectors which are supposed to freely explore the two grafting surfaces. We focus on the sphere-plane and sphere-sphere geometries. Because the chains are mobile, they are able to adapt both the local grafting density and their conformation to the position of the surfaces. Using a scaling approach, we show that, in chemical equilibrium, local grafting density is non-monotonic, and the junction can be divided into two different regions: the center, where connectors are compressed and exert a repulsive force between the objects (high excluded-volume interactions) and an external corona, where chains are stretched and attract the two objects. The relative importance of these regions varies for different separations and depends on surface geometries. When an external force is applied, this spatially inhomogeneous constraint exerted by the junction leads to specific force-distance profiles, which differ from profiles in the case of fixed connectors. An effective interaction potential and the adhesion energy are computed, showing a strong dependence on the geometry of surfaces.

Biophysical Phenomena↗
PubMed2002

Dietary salt supplementation selectively downregulates NPR-C receptor expression in kidney independently of ANP.

Atrial natriuretic peptide (ANP) has negative modulatory effects on a variety of pathophysiological mechanisms; i.e., it inhibits hypoxia-induced pulmonary vasoconstriction and vascular remodeling and facilitates natriuresis and vasorelaxation in NaCl-supplemented subjects. We have previously demonstrated organ-selective potentiation of ANP in the pulmonary circulation of hypoxia-adapted animals by local downregulation of its clearance receptor (NPR-C; Li H, Oparil S, Meng QC, Elton T, and Chen Y-F. Am J Physiol Lung Cell Mol Physiol 268: L328-L335, 1995). The present study tested the hypothesis that NPR-C expression is attenuated selectively in kidneys of NaCl-supplemented subjects. Adult male wild-type (ANP+/+) and homozygous mutant (ANP-/-) mice were studied after 5 wk of normal or high-salt diets. Mean arterial pressure (MAP) and left (LV) and right ventricular (RV) mass were greater in ANP-/- mice than in ANP+/+ mice fed the normal-salt diet; salt supplementation induced increases in plasma ANP in ANP+/+ mice and in MAP and LV, RV, and renal mass in ANP-/- mice but not in ANP+/+ mice. NPR-C mRNA levels were selectively and significantly reduced (>60%) in kidney, but not in lung, brain, LV, or RV, by dietary salt supplementation in both genotypes. NPR-A mRNA levels did not differ among diet-genotype groups in any organ studied. cGMP content was significantly increased in kidney, but not in lung or brain, by dietary salt supplementation in both genotypes. These findings suggest that selective downregulation of NPR-C in the kidney in response to dietary salt supplementation may contribute to local elevation in ANP levels and may be functionally significant in attenuating the development of salt-sensitive hypertension.

Animals↗
PubMed1999

Postnatal hemodynamic changes in very-low-birthweight infants.

The purpose of this study was to characterize postnatal changes in regional Doppler blood flow velocity (BFV) and cardiac function of very-low-birthweight infants and to examine factors that might influence these hemodynamic changes. Mean and end-diastolic BFV of the middle cerebral and superior mesenteric arteries, cardiac output, stroke volume, and fractional shortening were measured in 20 infants birthweight 1,002 +/- 173 g, gestational age 28 +/- 2 wk) at 6, 30, and 54 h after birth and before and after feedings on days 7 and 14. Postnatal increases in cerebral BFV, mesenteric BFV, and cardiac output were observed that were not associated with changes in blood pressure, hematocrit, pH, arterial PCO(2), or oxygen saturation. The postnatal pattern of relative vascular resistance (RVR) differed between the cerebral and mesenteric vasculatures. RVR decreased in the middle cerebral but not the superior mesenteric artery. Physiological patency of the ductus arteriosus did not alter postnatal hemodynamic changes. In response to feeding, mesenteric BFV and stroke volume increased, and mesenteric RVR and heart rate decreased. Postprandial responses were not affected by postnatal age or the age at which feeding was initiated. However, the initiation of enteral nutrition before 3 days of life was associated with higher preprandial mesenteric BFV and lower mesenteric RVR than was later initiation of feeding. We conclude that in very-low-birthweight infants over the first week of life 1) systemic, cerebral, and mesenteric hemodynamics exhibit region-specific changes; 2) asymptomatic ductus arteriosus patency and early feedings do not significantly influence these postnatal hemodynamic changes; and 3) cardiac function adapts to increase local mesenteric BFV in response to feedings.

Blood Flow Velocity↗
PubMed1985

Comparative electrophysiology of pyramidal and sparsely spiny stellate neurons of the neocortex.

Slices of sensorimotor and anterior cingulate cortex from guinea pigs were maintained in vitro and bathed in a normal physiological medium. Electrophysiological properties of neurons were assessed with intracellular recording techniques. Some neurons were identified morphologically by intracellular injection of the fluorescent dye Lucifer yellow CH. Three distinct neuronal classes of electrophysiological behavior were observed; these were termed regular spiking, bursting, and fast spiking. The physiological properties of neurons from sensorimotor and anterior cingulate areas did not differ significantly. Regular-spiking cells were characterized by action potentials with a mean duration of 0.80 ms at one-half amplitude, a ratio of maximum rate of spike rise to maximum rate of fall of 4.12, and a prominent afterhyperpolarization following a train of spikes. The primary slope of initial spike frequency versus injected current intensity was 241 Hz/nA. During prolonged suprathreshold current pulses the frequency of firing adapted strongly. When local synaptic pathways were activated, all cells were transiently excited and then strongly inhibited. Bursting cells were distinguished by their ability to generate endogenous, all-or-none bursts of three to five action potentials. Their properties were otherwise very similar to regular-spiking cells. The ability to generate a burst was eliminated when the membrane was depolarized to near the firing threshold with tonic current. By contrast, hyperpolarization of regular-spiking (i.e., nonbursting) cells did not uncover latent bursting tendencies. The action potentials of fast-spiking cells were much briefer (mean of 0.32 ms) than those of the other cell types.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1998

Kernel-Based Equiprobabilistic Topographic Map Formation.

We introduce a new unsupervised competitive learning rule, the kernel-based maximum entropy learning rule (kMER), which performs equiprobabilistic topographic map formation in regular, fixed-topology lattices, for use with nonparametric density estimation as well as nonparametric regression analysis. The receptive fields of the formal neurons are overlapping radially symmetric kernels, compatible with radial basis functions (RBFs); but unlike other learning schemes, the radii of these kernels do not have to be chosen in an ad hoc manner: the radii are adapted to the local input density, together with the weight vectors that define the kernel centers, so as to produce maps of which the neurons have an equal probability to be active (equiprobabilistic maps). Both an "online" and a "batch" version of the learning rule are introduced, which are applied to nonparametric density estimation and regression, respectively. The application envisaged is blind source separation (BSS) from nonlinear, noisy mixtures.

Journal Article↗
PubMed2002

Collagen deposition in HIV-1 infected lymphatic tissues and T cell homeostasis.

Lymphatic tissues (LTs) are structurally organized to promote interaction between antigens, chemokines, growth factors, and lymphocytes to generate an immunologic response and maintain normal-sized populations of CD4(+) and CD8(+) T cells. Inflammation and tissue remodeling that accompany local innate and adaptive immune responses to HIV-1 replication cause damage to the LT architecture. As a result, normal populations of CD4(+) and CD8(+) T cells cannot be supported and antigen-lymphocyte interactions are impaired. This conclusion is supported herein following LT sampling before and during anti-HIV therapy in persons with acute, chronic, and late-stage HIV-1 infection. Among seven individuals treated with anti-retroviral therapy (ART) and four individuals deferring therapy we found evidence of significant paracortical T cell zone damage associated with deposition of collagen, the extent of which was inversely correlated with both the size of the LT CD4(+) T cell population and the change in peripheral CD4(+) T cell count with anti-HIV therapy. The HIV-1-associated inflammatory changes and scarring in LT both limit the ability of the tissue to support and reestablish normal-sized populations of CD4(+) T cells and suggest a novel mechanism of T cell depletion that may explain the failure of ART to significantly increase CD4(+) T cell populations in some HIV-1-infected persons.

Antiretroviral Therapy, Highly Active↗
PubMed2004

Genetic analyses of a seasonal interval timer.

Seasonal clocks (e.g., circannual clocks, seasonal interval timers) permit anticipation of regularly occurring environmental events by timing the onset of seasonal transitions in reproduction, metabolism, and behavior. Implicit in the concept that seasonal clocks reflect adaptations to the local environment is the unexamined assumption that heritable genetic variance exists in the critical features of such clocks, namely, their temporal properties. These experiments quantified the intraspecific variance in, and heritability of, the photorefractoriness interval timer in Siberian hamsters (Phodopus sungorus), a seasonal clock that provides temporal information to mechanisms that regulate seasonal transitions in body weight. Twenty-seven families consisting of 54 parents and 109 offspring were raised in a long-day photoperiod and transferred as adults to an inhibitory photoperiod (continuous darkness; DD). Weekly body weight measurements permitted specification of the interval of responsiveness to DD, a reflection of the duration of the interval timer, in each individual. Body weights of males and females decreased after exposure to DD, but 3 to 5 months later, somatic recrudescence occurred, indicative of photorefractoriness to DD. The interval timer was approximately 5 weeks longer and twice as variable in females relative to males. Analyses of variance of full siblings revealed an overall intraclass correlation of 0.71 +/- 0.04 (0.51 +/- 0.10 for male offspring and 0.80 +/- 0.06 for female offspring), suggesting a significant family resemblance in the duration of interval timers. Parent-offspring regression analyses yielded an overall heritability estimate of 0.61 +/- 0.2; h(2) estimates from parent-offspring regression analyses were significant for female offspring (0.91 +/- 0.4) but not for male offspring (0.35 +/- 0.2), indicating strong additive genetic components for this trait, primarily in females. In nature, individual differences, both within and between sexes, in the timekeeping properties of seasonal interval timers, and a strong heritable basis thereof, would provide ample substrate for selection to rapidly influence seasonal clocks. Balancing selection in environments where the onset of spring conditions varies from year to year could maintain genetic variance in interval timers and yield interval timers tuned to the local environment.

Animals↗
PubMed2004

Collective violence: comparisons between youths and chimpanzees.

Patterns of collective violence found among humans include similarities to those seen among chimpanzees. These include participation predominantly by males, an intense personal and group concern with status, variable subgroup composition, defense of group integrity, inter-group fights that include surprise attacks, and a tendency to avoid mass confrontation. Compared to chimpanzee communities, youth gangs tend to be larger, composed of younger individuals, occupying smaller territories and having a more complex organization. Youth gangs also differ from chimpanzee communities as a result of numerous cultural and environmental influences including complex relations with non-gang society. These relations are governed in important ways by such factors as perceived economic and personal constraints, policing, family structure, and levels of poverty, crime, and racism. Nevertheless, the concepts that sociologists use to account for collective violence in youth gangs are somewhat similar to those applied by anthropologists and biologists to chimpanzees. Thus in both cases collective violence is considered to emerge partly because males are highly motivated to gain personal status, which they do by physical violence. In the case of youth gangs, the reasons for the prevalence of physical violence in status competition compared to non-gang society are clearly context-specific, both culturally and historically. By contrast, among chimpanzees the use of physical violence to settle status competition is universal (in the wild and captivity). The use of physical violence in individual status competition therefore has different sources in youth gangs and chimpanzees. Regardless of its origin, however, its combination with an intense concern for status can explain: (1) why individual males form alliances among each other; and hence (2) how such alliances generate social power, closed groups, and a capacity for defense of territory or pre-emptive attacks on rivals. This comparison suggests that the use of physical violence to resolve individual status competition is an important predictor of collective violence at the gang level. We therefore view the similarities in aggression between humans and chimpanzees that we review here as being adaptive responses to local conditions, predicated on an inherent male concern for social status.

Adolescent↗