Phenotypic and genetic associations between gray matter covariation and tool use skill in chimpanzees (Pan troglodytes): Repeatability in two genetically isolated populations.

Humans and chimpanzees both exhibit a diverse set of tool use skills which suggests selection for tool manufacture and use occurred in the common ancestors of the two species. Our group has previously reported phenotypic and genetic associations between tool use skill and gray matter covariation, as quantified by source-based morphometry (SBM), in chimpanzees. As a follow up study, here we evaluated repeatability in heritability in SBM components and their phenotypic association with tool use skill in two genetically independent chimpanzee cohorts. Within the two independent cohorts of chimpanzees, we identified 8 and 16 SBM components, respectively. Significant heritability was evident for multiple SBM components within both cohorts. Further, phenotypic associations between tool use performance and the SBM components were largely consistent between the two cohorts; the most consistent finding being an association between tool use performance and an SBM component including the posterior superior temporal sulcus (STS) and superior temporal gyrus (STG), and the interior and superior parietal regions (p < 0.05). These findings indicate that the STS, STG, and parietal cortices are phenotypically and genetically implicated in chimpanzee tool use abilities.

Comparative analysis of encephalization in mammals reveals relaxed constraints on anthropoid primate and cetacean brain scaling.

There is a well-established allometric relationship between brain and body mass in mammals. Deviation of relatively increased brain size from this pattern appears to coincide with enhanced cognitive abilities. To examine whether there is a phylogenetic structure to such episodes of changes in encephalization across mammals, we used phylogenetic techniques to analyse brain mass, body mass and encephalization quotient (EQ) among 630 extant mammalian species. Among all mammals, anthropoid primates and odontocete cetaceans have significantly greater variance in EQ, suggesting that evolutionary constraints that result in a strict correlation between brain and body mass have independently become relaxed. Moreover, ancestral state reconstructions of absolute brain mass, body mass and EQ revealed patterns of increase and decrease in EQ within anthropoid primates and cetaceans. We propose both neutral drift and selective factors may have played a role in the evolution of brain-body allometry.

Age-related differences in corpus callosum area of capuchin monkeys.

Capuchin monkeys (Cebus apella) are New World primates with relatively large brains for their body size. The developmental trajectories of several brain regions-including cortical white matter, frontal lobe white matter, and basal ganglia nuclei-are similar to humans. Additionally, capuchins have independently evolved several behavioral and anatomical characteristics in common with humans and chimpanzees-including complex manipulative abilities, use of tools, and the use of precision grips-making them interesting species for studies of comparative brain morphology and organization. Here, we report the first investigation into the development of the corpus callosum (CC) and its regional subdivisions in capuchins. CC development was quantified using high-resolution structural magnetic resonance imaging (MRI) images from 39 socially reared subjects (male n=22; female n=18) ranging in age from 4 days (infancy) to 20 years (middle adulthood). The total area of the CC and the subdivisions of the genu, rostral midbody, medial midbody, caudal midbody, and splenium were traced from the midsagittal section. Total CC area displayed significant differences across this time span and was best explained by quadratic growth. Sustained linear growth was observed in the subdivisions of the genu, rostral midbody, and splenium; sustained quadratic growth was seen in the subdivision of the medial midbody. Differences in growth were not detected in the subdivision of the caudal midbody. Females had a larger raw area of the total CC and of the medial midbody and caudal midbody throughout the lifespan. Our results indicate that capuchins show continued white matter development beyond adolescence in regions related to cognitive and motor development.

Comparative analysis of the nucleus basalis of Meynert among primates.

Long projection axons from the Ch4 cell group of the nucleus basalis of Meynert (nbM) provide cholinergic innervation to the neurons of the cerebral cortex. This cortical cholinergic innervation has been implicated in behavioral and cognitive functions, including learning and memory. Recent evidence revealed differences among primate species in the pattern of cholinergic innervation specific to the prefrontal cortex. While macaques displayed denser cholinergic innervation in layers I and II relative to layers V and VI, in chimpanzees and humans, layers V and VI were as heavily innervated as the supragranular layers. Furthermore, clusters of cholinergic axons were observed within the prefrontal cortex of both humans and chimpanzees to the exclusion of macaque monkeys, and were most commonly seen in humans. The aim of the present study was to determine whether the Ch4 cell group was modified during evolution of anthropoid primates as a possible correlate of these changes in cortical cholinergic innervation. We used stereologic methods to estimate the total number of choline acetyltransferase-immunoreactive magnocellular neurons within the nbM of New World monkeys, Old World monkeys, apes, and humans. Linear regression analyses were used to examine the relationship of the Ch4 cell group with neocortical volume and brain mass. Results showed that total nbM neuron numbers hyposcale relative to both neocortical volume and brain mass. Notably, the total number of nbM neurons in humans were included within the 95% confidence intervals for the prediction generated from nonhuman data. In conclusion, while differences in the cholinergic system exist among primate species, such changes appear to involve mostly axon collateral terminations within the neocortex and, with the exception of the relatively small group of cholinergic cells of the subputaminal subdivision of the nbM at the anterointermediate and rostrolateral levels, are not accompanied by a significant extra-allometric increase in the overall number of subcortical neurons that provide that innervation.

Species-specific distributions of tyrosine hydroxylase-immunoreactive neurons in the prefrontal cortex of anthropoid primates.

In this study, we assessed the distribution of cortical neurons immunoreactive for tyrosine hydroxylase (TH) in prefrontal cortical regions of humans and nonhuman primate species. Immunohistochemical methods were used to visualize TH-immunoreactive (TH-ir) neurons in areas 9 (dorsolateral prefrontal cortex) and 32 (anterior paracingulate cortex). The study sample included humans, great apes (chimpanzee, bonobo, gorilla, orangutan), one lesser ape (siamang), and Old World monkeys (golden guenon, patas monkey, olive baboon, moor macaque, black and white colobus, and François' langur). The percentage of neurons within the cortex expressing TH was quantified using computer-assisted stereology. TH-ir neurons were present in layers V and VI and the subjacent white matter in each of the Old World monkey species, the siamang, and in humans. TH-ir cells were also occasionally observed in layer III of human, siamang, baboon, colobus, and François' langur cortex. Cortical cells expressing TH were notably absent in each of the great ape species. Quantitative analyses did not reveal a phylogenetic trend for percentage of TH-ir neurons in these cortical areas among species. Interestingly, humans and monkey species exhibited a bilaminar pattern of TH-ir axon distributions within prefrontal regions, with layers I-II and layers V-VI having the densest contingent of axons. In contrast, the great apes had a different pattern of laminar innervation, with a remarkably denser distribution of TH-ir axons within layer III. It is possible that the catecholaminergic afferent input to layer III in chimpanzees and other great apes covaries with loss of TH-ir cells within the cortical mantle.

Cortical dopaminergic innervation among humans, chimpanzees, and macaque monkeys: a comparative study.

In this study, we assessed the possibility that humans differ from other primate species in the supply of dopamine to the frontal cortex. To this end, quantitative comparative analyses were performed among humans, chimpanzees, and macaques using immunohistochemical methods to visualize tyrosine hydroxylase-immunoreactive axons within the cerebral cortex. Axon densities and neuron densities were quantified using computer-assisted stereology. Prefrontal areas 9 and 32 were chosen for evaluation due to their roles in higher-order executive functions and theory of mind, respectively. Primary motor cortex (area 4) was also evaluated because it is not directly associated with cognition. We did not find an overt quantitative increase in cortical dopaminergic innervation in humans relative to the other primates examined. However, several differences in cortical dopaminergic innervation were observed among species which may have functional implications. Specifically, humans exhibited a sublaminar pattern of innervation in layer I of areas 9 and 32 that differed from that of macaques and chimpanzees. Analysis of axon length density to neuron density among species revealed that humans and chimpanzees together deviated from macaques in having increased dopaminergic afferents in layers III and V/VI of areas 9 and 32, but there were no phylogenetic differences in area 4. Finally, morphological specializations of axon coils that may be indicative of cortical plasticity events were observed in humans and chimpanzees, but not macaques. Our findings suggest significant modifications of dopamine's role in cortical organization occurred in the evolution of the apes, with further changes in the descent of humans.

Car safety seats for children: rear facing for best protection.

OBJECTIVE: To compare the injury risk between rear-facing (RFCS) and forward-facing (FFCS) car seats for children less than 2 years of age in the USA. METHODS: Data were extracted from a US National Highway Traffic Safety Administration vehicle crash database for the years 1988-2003. Children 0-23 months of age restrained in an RFCS or FFCS when riding in passenger cars, sport utility vehicles, or light trucks were included in the study. Logistic regression models and restraint effectiveness calculations were used to compare the risk of injury between children restrained in RFCSs and FFCSs. RESULTS: Children in FFCSs were significantly more likely to be seriously injured than children restrained in RFCSs in all crash types (OR=1.76, 95% CI 1.40 to 2.20). When considering frontal crashes alone, children in FFCSs were more likely to be seriously injured (OR=1.23), although this finding was not statistically significant (95% CI 0.95 to 1.59). In side crashes, however, children in FFCSs were much more likely to be injured (OR=5.53, 95% CI 3.74 to 8.18). When 1 year olds were analyzed separately, these children were also more likely to be seriously injured when restrained in FFCSs (OR=5.32, 95% CI 3.43 to 8.24). Effectiveness estimates for RFCSs (93%) were found to be 15% higher than those for FFCSs (78%). CONCLUSIONS: RFCSs are more effective than FFCSs in protecting restrained children aged 0-23 months. The same findings apply when 1 year olds are analyzed separately. Use of an RFCS, in accordance with restraint recommendations for child size and weight, is an excellent choice for optimum protection up to a child's second birthday.

Frontal sled tests comparing rear and forward facing child restraints with 1-3 year old dummies.

Although most countries recommend transitioning children from rear facing (RF) to forward facing (FF) child restraints at one year of age, Swedish data suggests that RF restraints are more effective. The objective of this study was to compare RF and FF orientations in frontal sled tests. Four dummies (CRABI 12 mo, Q1.5, Hybrid III 3 yr, and Q3) were used to represent children from 1 to 3 years of age. Restraint systems tested included both 1) LATCH and 2) rigid ISOFIX with support leg designs. Rear facing restraints with support legs provided the best results for all injury measures, while RF restraints in general provided the lowest chest displacements and neck loads.

Quantifying the relationship between vehicle interior geometry and child restraint systems.

The prevention of interactions of children or child restraints with other vehicle structures is critical to child passenger safety. Fifteen current vehicles and seven rear and forward facing child restraint systems were measured in an attempt to quantify the available distance between child restraints and these vehicle structures. Rear facing child restraints exhibited such small amounts of clearance that contact would be expected in the majority of frontal crashes. Upper tethers are critical in the prevention of head contact, while head contact is likely when the upper tether is not used.

Vehicle interior interactions and kinematics of rear facing child restraints in frontal crashes.

The performance of rear facing child restraints in frontal crashes can be determined by controlling a) the child's kinematics and b) interactions with vehicle structures. Twelve sled tests were performed to analyze the effect of the location and structural properties of vehicle interior components. The role of restraint kinematics was studied by developing computational models which underwent idealized motions. Stiff structures originally offset from the restraint, but which contact the restraint late in the test, cause increased injury values. Attachment methods which reduce child restraint rotation and more rigidly couple the restraint to the vehicle result in the best safety performance.

First glimpse of the functional benefits of clitoral hood piercings.

In this exploratory study, we identify a positive relationship between vertical clitoral hood piercing and desire, frequency of intercourse and arousal. There were no dramatic differences in orgasmic functioning. Clinicians can play key roles in educating patients about potential outcomes and risks of genital piercing.

The performance of various rear facing child restraint systems in a frontal crash.

Current forward facing (FF) child restraint designs use LATCH and ISOFIX systems to couple the restraint to the vehicle. Rear facing (RF) child restraints, however, have multiple coupling methods that vary by manufacturer and country of origin. Sled tests were performed with the CRABI 12 month dummy in six different RF attachment conditions. The performance of the rear facing child restraints (restraint kinematics, head accelerations, and neck loads) was highly dependent on the coupling method used. The results were also compared to a FF LATCH restraint.

Prediction of cervical spine injury risk for the 6-year-old child in frontal crashes.

This article presents a series of 49 km/h sled tests using the Hybrid III 6-year-old dummy in a high-back booster, a low-back booster, and a three-point belt. Although a 10-year review at a level I trauma center showed that noncontact cervical spine injuries are rare in correctly restrained booster-age children, dummy neck loads exceeded published injury thresholds in all tests. The dummy underwent extreme neck flexion during the test, causing full-face contact with the dummy's chest. These dummy kinematics were compared to the kinematics of a 12-year-old cadaver tested in a similar impact environment. The cadaver test showed neck flexion, but also significant thoracic spinal flexion which was nonexistent in the dummy. This comparison was expanded using MADYMO simulations in which the thoracic spinal stiffness of the dummy model was decreased to give a more biofidelic kinematic response. We conclude that the stiff thoracic spine of the dummy results in high neck forces and moments that are not representative of the true injury potential.

Prediction of cervical spine injury risk for the 6-year-old child in frontal crashes.

This paper presents a series of 49 km/h sled tests using the Hybrid III 6-year-old dummy in a high-back booster, a low-back booster, and a three-point belt. Although it is shown that non-contact cervical spine injuries are rare in correctly restrained children in this age group, neck loads exceeded published injury thresholds in all tests. The dummy kinematics were compared to the kinematics of a 12-year-old cadaver tested in a similar impact environment. This comparison was expanded using MADYMO simulations. It is concluded that the stiff thoracic spine of the dummy results in high neck forces and moments that are not representative of the true injury potential.

Characterization of high density monolayers of the biofilm bacterium Caulobacter crescentus: evaluating prospects for developing immobilized cell bioreactors.

Caulobacters are biofilm-forming members of the natural flora of soil and aquatic environments, which exhibit several characteristics that make them attractive for development of high surface area microbial bioreactors or biosensors. Although caulobacters are well characterized genetically, little is known about their biofilm-forming characteristics as a monoculture, or their tolerance of bioreactor-like conditions. Here we investigated the ability of caulobacters to spontaneously form high-density monolayers on artificial surfaces under a variety of environmental conditions, using phase contrast image analysis to assess biofilm density, and epifluorescence with the vital stain DiBAC to assess viability. With adequate nutrition, extremely dense monolayers formed within 24-48 h, and maintained near 100% viability in experiments ranging up to 22 days. When areas were abraded to remove cells, repopulation occurred rapidly with characteristics similar to the population of a clean surface. When established monolayers were starved for nutrients, a significant fraction of the cells detached from the surface, and cells remaining on the surface no longer tested as viable. Within 4-6 h of nutrient restoration, however, cells in the monolayer again appeared normal and tested as 100% viable. This is the first demonstration that Caulobacter crescentus is stable and amenable to high density monolayer growth and resists starvation, though some cells may express a programmed response to detach from the surface under severe nutrient limitation.

Coronal suture response to distraction osteogenesis in rabbits with delayed-onset craniosynostosis.

Recent studies have identified a subpopulation of persons with craniosynostosis who exhibit progressive or delayed-onset synostosis and mild cranial vault deformities. These persons may be good candidates for nonextirpation distraction osteogenesis. The present studies were designed to determine force-displacement parameters and assess the effects of distraction osteogenesis on coronal suture growth and morphologic characteristics in a rabbit model with congenital, delayed-onset craniosynostosis. Data were collected from a total of 178 rabbits: 71 normal controls; 16 normal controls with distraction; 72 with delayed-onset coronal suture synostosis; and 19 with delayed-onset coronal suture synostosis and distraction. At 10 days of age, all rabbits had amalgam markers placed on both sides of the coronal suture. In the force-displacement study, force-displacement distractors were placed across the coronal suture and distracted acutely for 1.0 mm at 42 days of age. Force-displacement curves for the coronal suture were best described by a third-order polynomial regression equation for both normal and synostosed groups. Significant differences (P < 0.05) were found in the mean force necessary to distract a normal suture 1 mm in distance (13.72 kg) compared with a suture with delayed-onset synostosis (48.39 kg). A significant (P < 0.05) relationship was also found between the extent of synostosis and the distractive force in rabbits with delayed-onset synostosis. In the distraction study, internal distractors were fixed across the coronal suture at 25 days of age and percutaneously and intermittently activated at an average of 0.11 mm/day for 42 days (4.54 mm total). Serial radiographs were taken at 10, 25, 42, and 84 days of age. Results revealed that rabbits with delayed-onset synostosis and distraction had significantly (P < 0.01) more coronal suture growth rates compared with rabbits with delayed-onset synostosis and no distraction. Coronal sutures were harvested at 84 days of age for qualitative histologic examination. Normal, distracted coronal sutures showed widened sutural ligaments and thin, active osteogenic fronts. In contrast, distracted coronal sutures from rabbits with delayed-onset synostosis showed narrowed sutural ligaments, thickened and blunt osteogenic fronts, and increased collagen and bony matrix deposition compared with controls. Results suggest that distraction osteogenesis without corticotomy may be a treatment alternative in persons with progressive, delayed-onset synostosis. However, these preliminary data also suggest that distractive forces may accelerate or stimulate osteogenesis differentially in persons with craniosynostosis, possibly through an underlying genetic disorder of bone and cytokine regulation. These differential osteogenic responses to distraction, if validated clinically, will need to be taken into account when planning distraction rate and rhythm protocols for patients with craniosynostosis.

Simple reversed-phase high-performance liquid chromatography quantitation of ganciclovir in human serum and urine.

A fast, simple, and cost-effective HPLC method for the quantitation of the antiviral drug ganciclovir is described. The serum samples are extracted with perchloric acid and neutralized with potassium phosphate buffer, and urine samples are diluted with distilled water. A reversed-phase column with isocratic elution by 15 mM potassium phosphate buffer (pH 2.5) containing 0.25% acetonitrile is used to separate ganciclovir; quantitation is by UV absorbance at 254 nm. Total turnaround time is 22 min; more than 3000 samples can be run on a single column without loss of peak quality. The limit of quantitation is 0.05 micrograms/ml. Recoveries varied from 91 to 107% with coefficients of variation ranging from 0.387 to 7.95%.

Characterization of an oligonucleotide-binding fluorescent ligand for application in affinity purification of dsDNA.

The fluorescent probe PO-PRO-3 was investigated as a potential ligand for the affinity immobilization and purification of genomic or plasmid DNA fragments. Affinities and mechanisms for PO-PRO-3 binding to superhelical and linearized pUC 18 plasmid DNA were examined through measurement of binding isotherms, continuous-variation analysis, and DNA titrations. In addition, the effects of DNA conformation, protein and RNA contaminants, solvent polarity, and ionic strength are examined with the aim of optimizing binding and elution conditions and of assigning limits to the range of applicability of the affinity purification.

Nanogram-level micro-volume DNA assay based on the monomeric cyanine dye PO-PRO-3 iodide.

Several commercially available DNA-staining dyes can yield highly sensitive fluorimetric assays under optimized conditions. However, the high cost of most dyes, coupled with the need for elaborate or expensive instrumentation and/or mL sample volumes, makes assays of this type very costly for routine use. We present a rapid, highly sensitive double-stranded DNA assay based on the new and relatively inexpensive monomeric cyanine dye PO-PRO-3. This dye exhibits maximum excitation/emission wavelengths that are compatible with one of the standard filter sets available on multi-well plate fluorimeters such as the Pandex FCA. The assay does not depend on DNA tertiary structure and is relatively insensitive to protein contamination (up to 1 mg/mL protein), although the bound dye fluorescence does diminish significantly at ionic strengths above approximately 25 mM. Under the assay conditions described here, subnanogram detection limits (in 60-microL sample volumes) are achievable. This assay makes high-sensitivity DNA quantification cost-effective and convenient for many routine analytical applications.