Postnatal somatometry of the rat facial skeleton

Growth of the rat facial skeleton over a 40 day period from birth was examined relative to 8 length and 4 width parameters of animals subject to somatic growth retardation experimentally induced by overtaxing the maternal lactational capacity by means of excessively large cross-fostered litters. Least squares regression lines were calculated for the preweaning period (day 1-20); the postweaning period (day 21-40) and the total period (day 1-40), thereafter being recalculated into segmented regression lines relative to the physiological growth phases. Specific phases of growth activity were noted throughout the 40 days with those in the preweaning period showing a marked consistency concomitant with the maternal lactational ability and subsequent emergence of biological weaning. A consistent phasic growth spectrum with definitive breaks in continuity supports the original postulate (Brody, 1927) that growth curves consist of phases of exponential activity delineated by changes in growth rate. Due to the inclusion of both control and experimental samples, the breakage points of the phases marking the change of growth rate different and were therefore reciprocated by alterations of phasic duration. Phasic growth occurred in the postweaning period with some degree of variance which did not permit an assessment of the causation factors with sufficient validity. The postweaning period of the experimental sample exhibited varying degrees of growth recovery (catch-up) in the majority of the facial parameters. Covariance analysis of the parameters in most instances showed that the parameters, as defined, and the bone units incorporated within them manifested a characteristic growth response in each sample irrespective of the modifying influence of the environmental factors.     

Mouse strain identification by means of discriminant analysis using mandible measurements

Mouse strains were identified by the aid of discriminant functions obtained from discriminant analysis of values measured at 13 sites of the mandible. They consisted of nine inbred strains of mice, AA, DDD, DDK, DDY, DSD, KK, NC, RR, and SS, and one mutant strain, NC-brp, maintained exactly in the National Institute of Animal Health, Minstry of Agriculture, Forestry and Fisheries. As a result, the probability of erroneous discrimination was 1 head/246 head, or 0.41%, for the males and 2 head/238 head, or 0.84%, for the females. Therefore, almost all the mouse strains were identified correctly. These results seemed to indicate that the strains of mice would be identified more correctly than before, if the present method by the aid of discriminant functions was applied in addition to the methods of identification based on the coat color, biochemical marker-genes, and histocompatibility genes.     

Bone defects of the facial skeleton - replacement with biomaterials

The authors report on their experience with bone defect treatment following surgery of jaw-bone cysts. This is based on the use of cadaveric ground spongiosis saturated with tetracycline and metronidazol solution. The study shows the above mentioned material is very suitable for bone defect therapy, and cost effective. The results were verified by clinical and X-ray examination.     

The influence of alveolar structures on the torsional strain field in a gorilla corporeal cross-section

Anthropologists have often used mandibular torsional properties to make inferences about primate dietary adaptations. Most of the methods employed are based on assumptions related to periodontal and alveolar properties. This study uses the finite element method to evaluate some of these assumptions with a cross-section through the third molar of a gorilla. Results indicate that the properties of alveolar bone play an important role in determining the strain field. In comparison, the exact stiffness values of the periodontal ligaments seem to have a much smaller impact. Replacing the dental roots and periodontal ligaments with alveolar bone, however, has a significant influence on the strain field. It underestimates the maximum shear strain by about 28% along its periosteal aspect when alveoli are modeled as cortical bone. It overestimates the strain by a smaller amount when alveoli are modeled as trabecular bone.This study supports the assumption that primate mandibles behave like a closed-section under torsion under the limiting condition that the alveolar bone stiffness is more than half of the value of cortical bone; alveolar bone can then be modeled as cortical bone with a minimal loss of accuracy. In addition, this study suggests that the minimum cortical thickness should be considered for torsional strength. Finally, modeling accuracy can be significantly increased if both dental and periodontal structures can be realistically incorporated into mandibular biomechanical models. However, this may not be always feasible in studies of fossil mandibles. This is due mainly to the difficulties involved in estimating alveolar bone densities and in distinguishing boundaries between cortical bone, alveolar bone, periodontal ligaments, and dental roots in fossil specimens.     

Note on the venous drainage of the gorilla (Gorilla gorilla) diploe

One-quarter or more of gorilla skulls manifest a canonically unrecognized foramen in the dorsal parieto-occipital region. This orifice (foramen obelionicum) affords exit to a notably large 'emergent' vein (vena obehonicd) draining the cranial vault diploe. These correlated structures affirm the presence of a mechanism of vault diploe drainage supplementary to that basic to all gorilla crania. Their anatomy is described herein. It is possible that the vena obelionica represents a Breschet formation, known so far for the human diploe only.     

Negative effect of Hox gene expression on the development of the neural crest-derived facial skeleton

Diencephalic, mesencephalic and metencephalic neural crest cells are skeletogenic and derive from neural folds that do not express Hox genes. In order to examine the influence of Hox gene expression on skull morphogenesis, expression of Hoxa2, Hoxa3 and Hoxb4 in conjunction with that of the green fluorescent protein has been selectively targeted to the Hox-negative neural folds of the avian embryo prior to the onset of crest cell emigration. Hoxa2 expression precludes the development of the entire facial skeleton. Transgenic Hoxa2 embryos such as those from which the Hox-negative domain of the cephalic neural crest has been removed have no upper or lower jaws and no frontonasal structures. Embryos subjected to the forced expression of Hoxa3 and Hoxb4 show severe defects in the facial skeleton but not a complete absence of facial cartilage. Hoxa3 prevents the formation of the skeleton derived from the first branchial arch, but allows the development (albeit reduced) of the nasal septum. Hoxb4, by contrast, hampers the formation of the nasal bud-derived skeleton, while allowing that of a proximal (but not distal) segment of the lower jaw. The combined effect of Hoxa3 and Hoxb4 prevents the formation of facial skeletal structures, comparable with Hoxa2. None of these genes impairs the formation of neural derivatives of the crest. These results suggest that over the course of evolution, the absence of Hox gene expression in the anterior part of the chordate embryo was crucial in the vertebrate phylum for the development of a face, jaws and brain case, and, hence, also for that of the forebrain.     

Observations on the teeth of the mountain gorilla (Gorilla gorilla beringei)

Measurements of a sample of mountain gorilla (Gorilla gorilla beringei) teeth are presented: when compared with other Gorilla series, the dimensions of the maxillary teeth fall in the upper end of the observed range for the genus. All of the upper teeth except the canine show a greater sex difference in the bucco-lingual diameter than in the mesio-distal dimension. This is also true for the other hominoids which have been studied, man, the chimpanzee, and the orang-utan, but to a lesser degree in man and the chimpanzee.     

Toxicology analysis by means of the JSM-method

MOTIVATION: A model for learning potential causes of toxicity from positive and negative examples and predicting toxicity for the dataset used in the Predictive Toxicology Challenge (PTC) is presented. The learning model assumes that the causes of toxicity can be given as substructures common to positive examples that are not substructures of negative examples. This assumption results in the choice of a learning model, called the JSM-method, and a language for representing chemical compounds, called the Fragmentary Code of Substructure Superposition (FCSS). By means of the latter, chemical compounds are represented as sets of substructures which are 'biologically meaningful' from the expert point of view. RESULTS: The chosen learning model and representation language show comparatively good performance for the PTC dataset: for three sex/species groups the predictions were ROC optimal, for one group the prediction was nearly optimal. The predictions tend to be conservative (few predictions and almost no errors), which can be explained by the specific features of the learning model. AVAILABILITY: by request to finn@viniti.ru; serge@viniti.ru, http://ki-www2.intellektik.informatik.tu-darmstadt.de/~jsm/QDA.     

The ontogeny of sexual dimorphism in the facial skeleton of the African apes

This paper aims to test the contribution of ontogenetic scaling to sexual dimorphism of the facial skeleton in the African apes. Specifically, it addresses whether males and females of each species share a common postnatal ontogenetic shape trajectory for the facial skeleton. Where trajectories are found to differ, it is tested whether male and female trajectories: 1) diverge early, or 2) diverge later after sharing a common trajectory earlier in the postnatal period. Where ontogenetic shape trajectories are found to be shared, it is also tested whether males and females are ontogenetically scaled. This study uses geometric morphometric analyses of 28 landmarks from the facial skeletons of 137 G. g. gorilla (62 adults; 75 juveniles), 95 P. paniscus (34 adults; 61 juveniles), and 115 P. t. troglodytes (58 adults; 57 juveniles). On average, males and females share a common ontogenetic shape trajectory until around the eruption of the second permanent molars. In addition, for the same period, males and females in each species share a common ontogenetic scaling trajectory. After this period, males and females diverge both from each other and from the common juvenile ontogenetic shape and scaling trajectories within each species. Thus, the male and female facial skeleton shows ontogenetic scaling until around the point of the eruption of the second molar (i.e., around puberty and the development of secondary sexual characteristics), but subsequent sexual dimorphism occurs via divergent trajectories and not via ontogenetic scaling.     

Calibration of the mercury-in-silastic strain gauge in tendon load experiments

A calibration method is presented by which the signals of mercury-in-silastic strain gauges (MISS), implanted in the tendons of in vitro loaded equine hindlegs, were converted to tendon loads. The relationships between MISS-signals and tendon loads were obtained from tensile-force tests applied to the tendons. Special attention was paid to the correction of the MISS-signals for amplitude-shifts resulting from internal repositioning of the MISS after tendon isolation and temperature differences. Shift corrections equivalent to tendon strains up to 2.8% were necessary in the in vitro experiment. The tendon loads deduced from the corrected MISS-signals were checked by torque analyses of the lower part of the limb. Differences between computed and experimentally obtained values of the torque of the tendon loads with respect to the fetlock joint ranged from -4 to +13%.