Within-group social relationships among females and adult males in wild western lowland gorillas (Gorilla gorilla gorilla)

Within-group female relationships, and relationships between females and adult males have not been described for wild western lowland gorillas. New data are presented here from Mbeli Bai in the Nouabale-Ndoki National Park, Republic of Congo. Nine groups were observed over a continuous 2-year period, and affiliative and agonistic interactions, as well as time spent by females and adult males in proximity to each other were recorded. Affiliative behavior was extremely rare in the bai, and measures of proximity between individuals were inconclusive because of the small sample sizes. Rates of agonistic interaction among females were highly variable between groups. The majority of agonistic interactions were undecided, and the supplant rate was low. Evidence for an agonistic dominance hierarchy is weak. The data do not support hypotheses that increased frugivory in western lowland gorillas raises levels of within-group contest competition; however, the need for intersite comparisons is stressed. In contrast, rates of agonistic behavior between females and silverback males were higher and more consistent between groups. Agonistic relationships between males and females conformed with patterns seen in mountain gorillas, where male protection from intraspecific aggression is important. The benefit females gain by forming long-term cooperative alliances appears to be small, and is likely outweighed by reproductive advantages associated with male protection.     

Root anchorage of inner and edge trees in stands of Maritime pine (<Emphasis Type="Italic">Pinus pinaster</Emphasis> Ait.) growing in different podzolic soil conditions

Static winching tests were carried out in order to determine the mechanical resistance of Maritime pine to overturning. The tested stands were selected according to podzolic soil conditions: wet Lande, characterised by a shallow ground water table and a hard pan horizon, and dry Lande, with a deeper ground water table and a hard pan absent or broken up. As this soil horizon limits the vertical growth of tree roots, anchorage resistance was investigated with regards to the presence or absence of a hard pan underneath each tree. To determine if mechanical behaviour differed within a stand, trees from inside the stand and edge trees at the border exposed to prevailing winds were also tested. The critical turning moment (TM_crit,total) at the base of the stem was positively related to the variable (H × DBH²) (H, total tree height; DBH, tree diameter). Linear regression analyses between TM_crit,total and (H × DBH²) showed that the presence of a hard pan had no significant effect on anchorage resistance in uprooted trees. Stem failure occurred for 82% of trees on dry Lande when (H × DBH²) < 1 m³. Moreover, stem failure type on dry Lande indicated that trees were better anchored. On soil with a hard pan, edge trees were found to be 20% more resistant to overturning than inner trees. Edge trees differed from inner trees in that the soil-root plate was two times larger and also possessed a larger surface area on the windward side.     

Comparison of the epidemiology, drug resistance mechanisms, and virulence of Candida dubliniensis and Candida albicans

Candida dubliniensis is a pathogenic yeast species that was first identified as a distinct taxon in 1995. Epidemiological studies have shown that C. dubliniensis is prevalent throughout the world and that it is primarily associated with oral carriage and oropharyngeal infections in human immunodeficiency virus (HIV)-infected and acquired immune deficiency syndrome (AIDS) patients. However, unlike Candida albicans, C. dubliniensis is rarely found in the oral microflora of normal healthy individuals and is responsible for as few as 2% of cases of candidemia (compared to approximately 65% for C. albicans). The vast majority of C. dubliniensis isolates identified to date are susceptible to all of the commonly used antifungal agents, however, reduced susceptibility to azole drugs has been observed in clinical isolates and can be readily induced in vitro. The primary mechanism of fluconazole resistance in C. dubliniensis has been shown to be overexpression of the major facilitator efflux pump Mdr1p. It has also been observed that a large number of C. dubliniensis strains express a non-functional truncated form of Cdr1p, and it has been demonstrated that this protein does not play a significant role in fluconazole resistance in the majority of strains examined to date. Data from a limited number of infection models reflect findings from epidemiological studies and suggest that C. dubliniensis is less pathogenic than C. albicans. The reasons for the reduced virulence of C. dubliniensis are not clear as it has been shown that the two species express a similar range of virulence factors. However, although C. dubliniensis produces hyphae, it appears that the conditions and dynamics of induction may differ from those in C. albicans. In addition, C. dubliniensis is less tolerant of environmental stresses such as elevated temperature and NaCl and H(2)O(2) concentration, suggesting that C. albicans may have a competitive advantage when colonising and causing infection in the human body. It is our hypothesis that a genomic comparison between these two closely-related species will help to identify virulence factors responsible for the far greater virulence of C. albicans and possibly identify factors that are specifically implicated in either superficial or systemic candidal infections.     

Biomechanical modeling of posterior instrumentation of the scoliotic spine

Scoliosis is a three-dimensional deformation of the spine that can be treated by vertebral fusion using surgical instrumentation. However, the optimal configuration of instrumentation remains controversial. Simulating the surgical maneuvers with personalized biomechanical models may provide an analytical tool to determine instrumentation configuration during the pre-operative planning. Finite element models used in surgical simulations display convergence difficulties as a result of discontinuities and stiffness differences between elements. A kinetic model using flexible mechanisms has been developed to address this problem, and this study presents its use in the simulation of Cotrel-Dubousset Horizon surgical maneuvers. The model of the spine is composed of rigid bodies corresponding to the thoracic and lumbar vertebrae, and flexible elements representing the intervertebral structures. The model was personalized to the geometry of three scoliotic patients (with a thoracic Cobb angle of 45 degrees, 49 degrees and 39 degrees ). Binary joints and kinematic constraints were used to represent the rod-implant-vertebra joints. The correction procedure was simulated using three steps: (1) Translation of hooks and screws on the first rod; (2) 90 degrees rod rotation; (3) Hooks and screws look-up on the rod. After the simulation, slight differences of 0-6 degrees were found for the thoracic spine scoliosis and the kyphosis, and of 1-8 degrees for the axial rotation of the apical vertebra and for the orientation of the plane of maximum deformity, compared to the real post-operative shape of the patient. Reaction loads at the vertebra-implant link were mostly below 1000 N, while reaction loads at the boundary conditions (representing the overall action of the surgeon) were in the range 7-470 N and maximum torque applied to the rod was 1.8 Nm. This kinetic modeling approach using flexible mechanisms provided a realistic representation of the surgical maneuvers. It may offer a tool to predict spinal geometry correction and assist in the pre-operative planning of surgical instrumentation of the scoliotic spine.     

Capillary electrophoresis as a method to study DNA reassociation

To develop analytical methodology to assess the genetic complexity of a DNA sample, capillary electrophoresis with laser-induced fluorescence detection is used to monitor the annealing process of DNA samples. Coated columns are filled with an entangled polymer solution shown to optimally separate DNA through size-selective capillary electrophoresis. DNA samples are denatured by heating in a boiling water bath for approximately 10 min and then cooled to approximately 25 degrees C below the melting point of the DNA sample to initiate the reassociation process. The DNA is detected by means of the laser-induced fluorescence of intercalated ethidium bromide, which produces a substantially greater signal for double- versus single-stranded DNA. The rate of reassociation is dependent upon the rate at which complimentary strands of DNA encounter each other and the degree of repeating base sequences in the sample (hence, the diversity of the DNA). Experimental parameters also influence the reassociation rate. The effects of salt concentration and incubation temperature are presented. Traditional plots of C(o)t (C(o) = DNA concentration and t = reassociation time) versus % recovery of double-stranded DNA signal are generated for PhiX 174 Hae III digest and 50 bp stepladder DNA, individually and combined, to calculate the reassociation rate constants for these samples. Because reassociation of individual fragments is observed by the CE-LIF method, more information about the samples is available than with less specific and time-consuming traditional methods of investigating DNA reassociation.     

A simple (14)C-respirometric method for assessing microbial catabolic potential and contaminant bioavailability

This paper describes the validation and application of a simple flask-based (14)C-respirometer system designed to assess mineralisation of (14)C-labelled substrates under defined conditions. Validation of this respirometer system indicated stoichiometric CO(2) trapping up to a maximum of 400 micromol of CO(2) (in a single trap). Polycyclic aromatic hydrocarbon (PAH)-degrading bacteria were used to measure growth-linked biodegradation of [(14)C]naphthalene to (14)CO(2). A (14)C activity balance of 101.7+/-8.9% (n=6), after 74 h incubation time and 10 respirometer-opening events, indicated the suitability of the system for monitoring substrate mineralisation. This respirometric apparatus was then successfully applied to assess: (i) the PAH catabolism of microbes in a field contaminated soil, where naphthalene and phenanthrene were rapidly mineralised and (ii) soil-associated organic contaminant bioavailability, where increased soil-phenanthrene contact time resulted in a reduction in phenanthrene mineralisation in the soil. The described respirometer system differs from existing respirometer systems in that the CO(2) trap can be removed and replaced quickly and easily. The system is efficient, reproducible, adaptable to many situations, easy to construct and simple to use, it therefore affords advantages over existing systems.     

Two-dimensional display and whole genome comparison of bacterial pathogen genomes of high G+C DNA content

Three highly mutable loci of the wall-less pathogens Mycoplasma bovis, Mycoplasma pulmonis and Mycoplasma agalactiae undergo high-frequency genomic rearrangements and generate extensive antigenic variation of major surface lipoproteins. Adjacent to each locus, an open reading frame exists as a single chromosomal copy and is predicted to encode a site-specific DNA recombinase exhibiting high homology to the recombinases XerD of Escherichia coli and CodV of Bacillus subtilis. Each of the mycoplasmal proteins are members of the lambda integrase family of tyrosine site-specific recombinases and likely mediates site-specific DNA inversions observed within the adjacent, variable loci.     

A structural model for the catalytic cycle of Ca(2+)-ATPase

Ca(2+)-ATPase is responsible for active transport of calcium ions across the sarcoplasmic reticulum membrane. This coupling involves an ordered sequence of reversible reactions occurring alternately at the ATP site within the cytoplasmic domains, or at the calcium transport sites within the transmembrane domain. These two sites are separated by a large distance and conformational changes have long been postulated to play an important role in their coordination. To characterize the nature of these conformational changes, we have built atomic models for two reaction intermediates and postulated the mechanisms governing the large structural changes. One model is based on fitting the X-ray crystallographic structure of Ca(2+)-ATPase in the E1 state to a new 6 A structure by cryoelectron microscopy in the E2 state. This fit indicates that calcium binding induces enormous movements of all three cytoplasmic domains as well as significant changes in several transmembrane helices. We found that fluorescein isothiocyanate displaced a decavanadate molecule normally located at the intersection of the three cytoplasmic domains, but did not affect their juxtaposition; this result indicates that our model likely reflects a native E2 conformation and not an artifact of decavanadate binding. To explain the dramatic structural effect of calcium binding, we propose that M4 and M5 transmembrane helices are responsive to calcium binding and directly induce rotation of the phosphorylation domain. Furthermore, we hypothesize that both the nucleotide-binding and beta-sheet domains are highly mobile and driven by Brownian motion to elicit phosphoenzyme formation and calcium transport, respectively. If so, the reaction cycle of Ca(2+)-ATPase would have elements of a Brownian ratchet, where the chemical reactions of ATP hydrolysis are used to direct the random thermal oscillations of an innately flexible molecule.     

The role of IFN in respiratory syncytial virus pathogenesis

Formalin-inactivated respiratory syncytial virus (RSV) vaccine preparations have been shown to cause enhanced disease in naive hosts following natural infection. In this study we demonstrate a similar pattern of enhanced disease severity following primary RSV infection of IFN-nonresponsive STAT1(-/-) mice. STAT1(-/-) mice showed markedly increased illness compared with wild-type BALB/c animals following RSV inoculation despite similar lung virus titers and rates of virus clearance. Histologically, STAT1(-/-) animals had eosinophilic and neutrophilic pulmonary infiltrates not present in wild-type or IFN-gamma(-/-)-infected mice. In cytokine analyses of infected lung tissue, IFN-gamma was induced in both STAT1(-/-) and wild-type mice, with preferential IL-4, IL-5, and IL-13 induction only in the STAT1(-/-) animals. Eotaxin was detected in the lungs of both wild-type and STAT1(-/-) mice following infection, with a 1.7-fold increase over wild-type in the STAT1(-/-) mice. Using a peptide epitope newly identified in the RSV fusion protein, we were able to demonstrate that wild-type memory CD4(+) T cells stimulated by this peptide produce primarily IFN-gamma, while STAT1(-/-)CD4(+) cells produce primarily IL-13. These findings suggest that STAT1 activation by both type I (alphabeta) and type II (gamma) IFNs plays an important role in establishing a protective, Th1 Ag-specific immune response to RSV infection.