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Exploring northeast African metric craniofacial variation at the individual level: a comparative study using principal components analysis.
A principal components analysis was carried out on male crania from the northeast quadrant of Africa and selected European and other African series. Individuals, not predefined groups, were the units of study, while nevertheless keeping group membership in evidence. The first principal component seems to largely capture "size" variation in crania from all of the regions. The same general morphometric trends were found to exist within the African and European crania, although there was some broad separation along a cline. Anatomically, the second principal component captures predominant trends denoting a broader to narrower nasal aperture combined with a similar shape change in the maxilla, an inverse relation between face-base lengths ("projection") and base breadths, and a decrease in anterior base length relative to base breadth. The third principal component broadly describes trends within Africa and Europe: specifically, a change from a combination of a relatively narrower face and longer vault, to one of a wider face and shorter vault; it shows the northeast quadrant Africans along a cline with the other Africans. Stated in relative terms, the northeastern Africans tend to exhibit narrower bases in relationship to more projecting faces, and broader nasal areas than Europeans, although there is range of variation. Relative to the other African groups, they have narrower nasal areas and narrower faces in relationship to vault length. The crania from the northeast quadrant of Africa collectively demonstrate the greatest pattern of overlap with both Europeans and other Africans. Variation was found to be high in all series but greatest in the African material as a whole. Individuals from different geographical regions frequently plotted near each other, revealing aspects of variation at the level of individuals that is obscured by concentrating on the most distinctive facial traits once used to construct "types." The high level of African interindividual variation in craniometric pattern is reminiscent of the great level of molecular diversity found in Africa. These results, coupled with those of Y chromosome studies, may help generate hypotheses concerning the length of time over which recent craniometric variation emerged in Africa.
The relationship between cranial metric and nonmetric traits in the rhesus macaques from Cayo Santiago.
This study addresses the relationship between cranial metric variables and nonmetric traits using the skeletal sample of rhesus macaques from Cayo Santiago. Discriminant function analysis is used to study the metric differences between macaque crania grouped according to the presence or absence of nine nonmetric traits. The computation of total structure coefficients from the discriminant function analyses provides information regarding how closely each metric variable is related to the discriminant functions derived. Total structure coefficients have not been used previously in the study of the relationship between metric and nonmetric traits. The results of the analysis are interpreted using an explicit approach to cranial morphogenesis-functional cranial analysis. It is concluded that the relationship between cranial metric and nonmetric traits is explicable in terms of a common developmental pathway shared by the two types of traits. Identification of the specific etiology of nonmetric traits depends on future anatomical studies or organisms throughout the period of nonmetric trait development.
Live imaging and morphometric analysis of embryonic development in the ascidian Ciona intestinalis.
The ascidian Ciona intestinalis is one of the model organisms of choice for comparative investigations of chordate development and for unraveling the molecular mechanisms underlying morphogenesis and cell fate specification. Taking advantage of the availability of various genetically encoded fluorescent proteins and of defined cis-regulatory elements, we combined transient transgenesis with laser scanning confocal imaging to acquire and quantitate 3D time-lapse data from living Ciona embryos. We used Ciona tissue-specific enhancers to drive expression of spectrally distinct fluorescent protein reporters to label and simultaneously visualize axially and paraxially positioned mesodermal derivatives, as well as neural precursors in individual embryos. We observed morphogenetic movements, without perturbing development, from the early gastrula throughout the larval stage, including gastrulation, neurulation, convergent extension of the presumptive notochord, and tail elongation. These multidimensional data allowed us to establish a reference system of metrics to quantify key developmental events including blastopore closure and muscle extension. The approach we describe can be used to document morphogenetic cell and tissue rearrangements in living embryos and paves the way for a live digitized anatomical atlas of Ciona.
Internal calibration technique for HREM studies of nanoscale particles.
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Management of evolving map data: data structures and algorithms based on the framework map.
A consensus framework map of a chromosome is the single most useful map of the chromosome, because of the amount of information it holds as well as the quality of the supporting data backing the putative order of its objects. We describe data structures and algorithms to assist in framework map maintenance and to answer queries about order and distance on genomic objects. We show how these algorithms are efficiently implemented in a client-server relational database. We believe that our data structures are particularly suitable for databases to support collaborative mapping efforts that use heterogeneous methodologies. We summarize two applications that use these algorithms: CHROMINFO, a database specifically designed for framework map maintenance; and the shared client-server database for the chromosome 12 genome center.
Interconversion of grams and pounds in the range of fetal weights.
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Infant visual responses to pattern: which metric predicts best?
Visual fixations were recorded in newborn, 4-, and 8-week old human infants as they scanned displays that varied along several dimensions. These displays were designed to evaluate four metrics that have been theorized to control infant visual preference: Contour length, size, number, and a new metric, CVAL, based on Contour Variability, Amount, and Location. This latter metric reflects characteristics of the visual system that other metrics ignore. Both contour length and CVAL separately accounted for approximately 95% of looking-duration variance, a much larger portion than the other metrics considered; however, CVAL accounted for more looking variance than contour length when the number of lines and contour length were deconfounded, and uniquely accommodated a large orientation effect. Finally, several predictions were confirmed about characteristics of visual scanning. Retinal structure and natural scanning dispositions should be considered in accounts of infants' reactions to visual stimuli.
The metrical structure of aging (dissipative) systems.
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DHLAS: A web-based information system for statistical genetic analysis of HLA population data.
DHLAS (database HLA system) is a user-friendly, web-based information system for the analysis of human leukocyte antigens (HLA) data from population studies. DHLAS has been developed using JAVA and the R system, it runs on a Java Virtual Machine and its user-interface is web-based powered by the servlet engine TOMCAT. It utilizes STRUTS, a Model-View-Controller framework and uses several GNU packages to perform several of its tasks. The database engine it relies upon for fast access is MySQL, but others can be used a well. The system estimates metrics, performs statistical testing and produces graphs required for HLA population studies: (i) Hardy-Weinberg equilibrium (calculated using both asymptotic and exact tests), (ii) genetics distances (Euclidian or Nei), (iii) phylogenetic trees using the unweighted pair group method with averages and neigbor-joining method, (iv) linkage disequilibrium (pairwise and overall, including variance estimations), (v) haplotype frequencies (estimate using the expectation-maximization algorithm) and (vi) discriminant analysis. The main merit of DHLAS is the incorporation of a database, thus, the data can be stored and manipulated along with integrated genetic data analysis procedures. In addition, it has an open architecture allowing the inclusion of other functions and procedures.
Metric determination of sex from the humerus in a Guatemalan forensic sample.
The absence of population-specific standards for sex, age and stature estimation for rural Guatemala is problematic for the forensic analysis of skeletal remains recovered from clandestine graves attributed to the recent armed conflict in that country. In order to increase the reliability of the forensic analyses being undertaken in Guatemala, standards for metric determination of sex were developed. Data was collected on several bones; the results for the humerus are presented here. A sample of 118 complete humeri (68 male and 50 female) was studied; maximum length, maximum diameter of the head, circumference at midshaft, maximum diameter at midshaft, minimum diameter at midshaft and epicondylar breadth were measured and subjected to discriminant function analysis. The classification accuracies for the univariate functions range from 76.8% for the maximum diameter at midshaft to 95.5% for the maximum diameter of the head. The classification accuracy for the stepwise procedure was 98.2%.
Postural reaction during maximum grasping maneuvers using a hand dynamometer in healthy subjects.
The purpose of this study was to quantitatively evaluate spontaneous body sway during maximum grasping maneuver with a hand dynamometer, which we sometimes encounter in clinical practice. The postural reaction of the whole body during maximum grasping maneuver was analyzed in 26 right-handed healthy male volunteers using a three-dimensional motion analysis system (VICON system, Oxford Metrics, UK) and force plates. We found that the gravity center of the body moved toward the grasping side. Also, voluntary rotation of the trunk and flexion of the neck was observed during grasping on each side.
Metric and non-metric randomization methods, geographic variation, and the single-species hypothesis for Asian and African Homo erectus.
This paper proposes a statistical test of the single-species hypothesis using non-metric characters as a complement to statistical tests using more traditional metric characters. The sample examined is that of Asian and African Homo erectus. The paleoanthropological community is divided on the taxonomic distinction of these fossils, with workers arguing both for and against the species-level distinction between Asian and African populations. Previous arguments have focused on patterns of apparent morphological differentiation between the African and Asian cranial samples. To assess this question, three tests were performed that compared the range of variation in the fossil sample to a single-species group with a similar geographic distribution; this comparative sample was composed of 221 modern humans from Africa and Asia. For the first test, 23 metric characters were analyzed on the fossil and comparative samples. Using resampling procedures, the variation for these characters was examined, recreating 1000 samples from the human analogs and comparing the CV distributions of these samples to the CVs of the fossil group. The second test used the metric data to calculate a Euclidean distance between the African and Asian fossil samples. This distance was compared to a distribution of Euclidean distances calculated between 1000 randomly selected samples of African and Asian modern humans. For the third test, a grading scale was created for ten non-metric characters that encompassed the total morphological variation found in the fossil and modern human samples. The Manhattan distance between the Asian and African fossil samples was calculated and compared to a distribution of distances calculated between 1000 randomly selected samples of African and Asian moderns. The first two tests, using the metric data, failed to falsify the null hypothesis. However, in the third test, using non-metric data, the total Manhattan distance for the fossil sample approached the 100th percentile of the resampled distances calculated from the moderns. The implications of the contrasting results are discussed.
Proposal for a nomenclature for magnetic resonance imaging based measures of articular cartilage in osteoarthritis.
OBJECTIVE: Magnetic resonance imaging (MRI) of articular cartilage has evolved to be an important tool in research on cartilage (patho)physiology and osteoarthritis (OA). MRI provides a wealth of novel and quantitative information, but there exists no commonly accepted terminology for reporting these metrics. The objective of this initiative was to propose a nomenclature for definitions and names to be used in scientific communications and to give recommendations as to which minimal methodological information should be provided when reporting MRI-based measures of articular cartilage in OA. METHODS: An international group of experts with direct experience in MRI measurement of cartilage morphology or composition reviewed the existing literature. Through an iterative process that included a meeting with a larger group of scientists and clinicians (December 2nd, 2004, Chicago, IL, USA), they discussed, refined, and proposed a nomenclature for MRI-based measures of articular cartilage in OA. RESULTS: The group proposes a nomenclature that describes: (1) the anatomical location and (2) the structural feature being measured, each name consisting of a metric variable combined with a tissue label. In addition, the group recommends minimal methodological information that should be described. CONCLUSIONS: Utilization of this nomenclature should facilitate communication within the scientific community. Further, the uniform adoption of comprehensive nomenclature to describe quantitative MRI- features of articular cartilage should strengthen epidemiological, clinical, and pharmacological studies in OA.
An easy way to convert visual acuity measurements.
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Editorial: Quantities and units in clinical and research laboratories.
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Observer error and birthweight: digit preference in recording.
We investigated the presence of digit preference in the recording of birthweight by a retrospective analysis of an official dataset of birth registrations. All births occurring in the Province of Saskatchewan in Canada from 1981 to 1991, but excluding 1988, were considered for this analysis. Preference for the terminal digit 0 increased progressively with increasing birthweight over the whole range of birthweights. Correction for digit preference led to an increase of 1.8% in the number of low birthweight babies and a concomitant increase of 0.1% in the actual incidence of low birthweight. Epidemiological applications of birthweight should take into account the observer error caused by digit preference.