Computer-assisted 3D reconstruction of serial sections of cortical bone to determine the 3D structure of osteons.

The objective of this study was to create three-dimensional (3D) images for the histomorphological study of osteons. Medical imaging technology was used to register digitized 2D images of serial decalcified histological sections of bone, to segment the tissues of interest from the surrounding tissues, and to create 3D reconstructions from the segmented structures. Examination of the 3D reconstructions did not support suggestions in the literature that osteons have a spiraling organization. In contrast, the 3D reconstructions indicated that osteons have a complex pattern of organization that is dominated by branching. Examination of the reconstructions also suggested that osteons described in the literature as being dumbbell shaped are actually artifacts of the plane of sectioning. This study demonstrated the applicability of imaging and visualization technology developed for the 3D reconstruction of medical images to the reconstruction of digitized 2D images of serial sections of bone and additionally demonstrated the feasibility of using 3D reconstructions for the histomorphological study of osteons.

Microscopic investigations of areolar brow structure in nonhuman primates and of vermiculate brow structure in hominids.

The microscopic structure of bone of the brow region was studied in adult human crania showing the vermiculate surface pattern, and in immature nonhuman primates with an areolar surface. Serial sections from different parts of each brow sampled regional comparability. The human brow regions are basically similar, and differ from those of the other primates. The elevations and depressions of vermiculate surfaces are lamellar bone, usually covered by layers featuring Sharpey's fibers. In contrast, the immature nonhuman primates do not have continuous brow surface layers. Passageways to the interior are closely spaced and separated by irregular projections. These findings indicate that fossil and modern human vermiculate surfaces are not structurally equivalent to areolar brow surfaces observed in some immature nonhuman primates. Reports describing fossil hominid brow regions as composed of 'fine cancellous bone' are probably erroneous and give misleading interpretations of their development and function.

The dentition of the "old man" of La Chapelle-aux-Saints and inferences concerning Neandertal behavior.

It has been suggested that the fossil Neandertal from La Chapelle-aux-Saints was so toothless that he would have had to have his food pre-chewed or otherwise prepared for him. This has also led to the inference that a high level of altruistic social behavior was characteristic of Neandertals. This appears to be in keeping with a current trend among anthropologists to upgrade the cultural and evolutionary status of Neandertals. Close examination of the recovered teeth and the condition of the alveoli indicates that the "old man" of La Chapelle-aux-Saints had upper and lower incisor, canine and premolar teeth on the left side intact and probably in occlusion, and that the same was true of these teeth in the right maxilla. Mandibular incisors, canine, and first premolar had probably been lost to a tumor or abscessing on the right side, but this pathology may have developed near the time of death. The right mandibular second premolar was probably functional, although tilted similarly to the intact premolar on the left. It is very unlikely that the individual was unable to chew food. The dentition thus gives no reliable evidence of altruistic behavior by his cohorts. This study may also relate to hypotheses concerning the ancestry of anatomically modern humans.

The development of the vermiculate pattern in the brow region of crania from Indian Knoll, Kentucky.

A convoluted brow surface consisting of fine ridges, grooves, and depressions, first identified in ancient fossil hominids and termed the vermiculate pattern (VP), is often low in frequency and of moderate rugosity in crania of anatomically modern human populations. Burials at Indian Knoll, Kentucky, constitute an excellent series for study of the development of the VP, since cranial surfaces are usually well preserved, there are hundreds of immature and mature individuals previously assessed for age, and the VP is high in frequency and rugosity. While a surface pattern resembling a miniature VP is found on the supraorbital surface of all newborns, it is not found on any children age 2 or older. This newborn pattern is probably different in structure and origin from the adult VP. The smooth surface characteristic of children shows evidence of changing to the VP in some adolescents, but the fullest development of the VP occurs in adults. The VP continues to develop in rugosity into the fourth decade, especially in males. These observations indicate that the human VP is different in etiology from somewhat similar brow surfaces found sporadically in immature individuals of some species of nonhuman primates. Statements lumping all vermiculate bone surfaces as "fine cancellous bone" are premature. The human VP development shows no apparent relationship to phases of tooth eruption, as postulated for the appearance of areolar surfaces on brow ridges of immature non-human primates.

Studies on the condition and structure of bone of the Saldanha fossil cranium.

The external surface of the Saldanha cranium shows extensive exfoliation and cracking. In a few places remnants of the probable original bone surfaces can be observed. These are orange-brown in color, contrasting with the nearly white color of exposed deeper layers, and are subdivided into small segments with pits in their centers. Causes of the color differences are uncertain but merit investigation. The surface cracking and exfoliation probably result from weathering before fossilization. This conclusion is based on the observation that the endocranial surfaces show no such effects, despite the scattering of the cranial fragments at the time of discovery. A depressed fracture in the frontal bone indicates a heavy blow at or shortly after the time of death. This blow probably created some of the fragments, but there are also incomplete fracture cracks which may have resulted from the blow. Unresolved taphonomic problems include the manner in which the cranium held together after decay of soft tissues allowed weathering, and the manner in which the fragments were subsequently scattered. Chips from the cranial vault indicate that the outer table was very thick, tending to support recent proposals that the specimen and assoicated fauna and tools are from a considerably earlier time period than originally believed. The surface damage to the brow ridges gives information on the structure of deeper layers. These are lacking orientation, supporting the hypothesis that hominid brow ridges are not primarily a response to masticatory forces, but may afford protection for the eyes.

The vermiculate surface pattern of brow ridges in Neandertal and modern crania.

A convoluted surface pattern of ridges and grooves characterizes the frontal torus in adult Neandertal fossils. Modern human skulls rarely have the pattern well developed. It is not observed in postcranial bones, nor in skulls of Neandertal children. This vermiculate bone is resistant to oriented cracking from weathering or fractures. Structural characteristics of the bone give evidence on the problem of the function of hominid brow ridges.

Three-dimensional studies on resorption spaces and developing osteons.

Resorption spaces and their continuations as developing osteons were traced in serial cross sections from decalcified long bones of dogs, baboons and a man, and from a human rib. Processes of formation of osteons and transverse (Volkmann's) canals can be inferred from three-dimensional studies. Deposits of new osseous tissue begin to line the walls of the spaces soon after termination of resorption. The first deposits are osteoid, usually stained very darkly by the silver nitrate procedure utilized, but a lighter osteoid zone adjacent to the canals occurs frequently. Osteoid linings continue to be produced as lamellar bone forms around them; the large canals of immature osteons usually narrow very gradually. Frequently they terminate both proximally and distally as resorption spaces, indicating that osteons often advance in opposite directions as they develop. Osteoclasts of resorption spaces tunnel preferentially into highly mineralized bone, and usually do not use previously existing canals as templates for their advance. Osteons evidently originate by localized resorption of one side of the wall of an existing vascular channel in bone, with subsequent orientation of the resorption front along the axis of the shaft. Advancing resorption spaces also apparently stimulate the formation of numerous additional transverse canal connections to neighboring longitudinal canals. Serial tracing and silver nitrate differential staining combine to reveal many of the processes of bone remodeling at work, and facilitate quantitative treatment of the data. Further uses in studies of bone tissue and associated cells are recommended.

Sequence of eruption of permanent teeth and epiphyseal union in three species of African monkeys.

Sequences of eruption of teeth and union of epiphyses determined for three species of African Cercopithecinae. These sequences are highly scalable and are highly comparable between among the species. Some sex differences in sequence were found within each species. The sequences of epiphyseal union in these species of Old World monkeys are very similar to published sequences in New World monkeys and other groups of higher primates. It appears that there is a single pattern common to the Anthropoidea as a whole.

Advanced weathering cracks as an improvement on split-line preparations for analysis of structural orientation in compact bone.

Weathering cracks have been demonstrated to be equivalent to split-lines in compact bone. The amount of cracking becomes more extensive with time. Advanced weathering cracks have the potential for giving more complete information on orientation patterns than split-lines. They can also be superior in accuracy and objectivity of results obtained, in preserving the original condition of the bone, and in elimination of much of the work involved in making split-line preparations.

Correspondence of silver nitrate staining patterns in decalcified bone withe the microradiographic image.

A procedure for differential staining of decalcified bone with silver nitrate showed major histological features which appeared to correspond closely to microradiographic images. The extent to which this is actually the case was investigated directly by preparing microradiographs of ground sections of baboon and dog radii and then decalcifying and staining the same sections. The many detailed similarities indicate that this staining procedure is a useful adjunct to microradiography. Thus, poorly mineralized osteons or layers of circumferential lamellae are darker stained by silver nitrate, and the variably mineralized layers of circumferential lamellae are closely duplicated by light and dark bands in the stained sections. These similarities imply that there is a relationship between the mineral density of bone and some condition of the organic matrix which is probably related to maturation changes in the collagen.