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T G Bromage

Publications and source records attributed to T G Bromage.

At least 19 recordsLinked to original sources
PubMed2005

Relationships among microstructural properties of bone at the human midshaft femur.

Mineralization density and collagen fibre orientation are two aspects of a bone's microstructural organization that influence its mechanical properties. Previous studies by our group have demonstrated a distinctly non-random, though highly variable, spatial distribution of these two variables in the human femoral cortex. In this study of 37 specimens, these variables are examined relative to one another in order to determine whether regions of bone demonstrating higher or lower mineralization density also demonstrate a prevalence of either transversely or longitudinally oriented collagen fibres. An analysis of rank-transformed collagen fibre orientation (as determined by circularly polarized light) and mineralization density (as determined by backscattered electron microscopy) data sets demonstrated that areas of low mineralization density (predominantly in the anterior-lateral cortex) tended to correspond to regions of higher proportions of longitudinally oriented collagen fibres. Conversely, areas of higher mineralization density (postero-medially) tended to correspond to regions of higher proportions of transversely oriented collagen fibres. High variability in the sample led to generally low correlations between the two data sets, however. A second analysis focused only on the orientation of collagen fibres within poorly mineralized bone (representing bone that was newly formed). This analysis demonstrated a lower proportion of transverse collagen fibres in newly formed bone with age, along with some significant regional differences in the prevalence of collagen fibres of either orientation. Again high variability characterized the sample. These results are discussed relative to the hypothesized forces experienced at the midshaft femur.

Adult↗
PubMed2003

Intrapopulation variability in mineralization density at the human femoral mid-shaft.

One of several microstructural variables known to affect the mechanical properties of bone is the degree of mineralization of bone matrix. The aim of this study was to examine mineralization density, and its variability with age and sex, from a biomechanical perspective. Histological sections, prepared from mid-shaft femora obtained at autopsy from 40 individuals, were imaged using quantitative backscattered electron microscopy. Each cross-section montage was divided into 48 segments according to anatomical position. Mean grey-level values were quantified for each segment. One-way ANOVA with Tukey HSD post hoc tests were used to test for differences in mineralization between segments, age groups and sexes. Results showed a decrease in overall degree of mineralization density with adult age, but an increase in its coefficient of variation. Degree of mineralization was significantly lower in the periosteal third of the cortex, particularly in the antero-lateral aspect. This pattern was most prevalent amongst the youngest individuals in the sample. Whereas males between ages 45-64 years had a higher average degree of mineralization than females, the opposite was true of the older age group. Mineralization significantly decreased between middle and older age groups in males, but not in females. Despite limited consistencies in the location of high and low average mineralization bone through the cortex, the degree of interindividual variation, even within a single age and sex group, overwhelmed population level trends. The patterns of variability identified in this study are consistent with results of an analysis of collagen fibre orientation using the same sample material.

Adult↗
PubMed2000

Effects of fetal exposure to nicotine on dental development of the laboratory rat.

Nicotine is one of the most widely used toxins in the world today. Most addiction research relating to nicotine in particular, as well as opioids and alcohol, has concentrated on the cellular and molecular biology of the mammalian brain and on features of organ structure and physiology associated with substance abuse. Thus, while numerous studies have been conducted to examine nicotine's detrimental physiological effects in a variety of soft tissues, this investigation attempts to examine further the gross morphological consequences of this drug on a hard tissue, the first molar crown of the laboratory rat. It is hypothesised that by providing nicotine to rats during and after the fetal cycle, changes in dental structure will occur, owing to perturbations of development induced by this toxin. The dentitions of Fisher rats exposed to nicotine during and after the fetal cycle, and those of their non-treated controls, were examined. By carefully measuring the length, width and occlusal (chewing) areas of the first maxillary molars, it was possible to identify any gross morphological effects of nicotine on dental development. It was found that dental asymmetries (calculated as a size difference between a tooth and its antimere) were significantly increased while occlusal areas were significantly decreased in nicotine-exposed rats compared to control rats. In addition, significant differences were detected within the experimental group, females tending to exhibit the deleterious effects of nicotine more so than males. These results are in accordance with the predicted outcome; in similar studies of physiological systems and soft tissues, dental development is affected by the presence of nicotine.

Animals↗
PubMed1995

Pattern of collagen fiber orientation in the ovine calcaneal shaft and its relation to locomotor-induced strain.

BACKGROUND: Gebhardt (1905. Arch. Entwickl. Org., 20:187-322) originated the hypothesis that the direction of collagen fibers in bone is a structural response to the type of mechanical load to which the bone is subjected. He proposed that collagen fibers aligned parallel to the loading axis are best suited to withstand tensile strain, whereas fibers oriented perpendicular to the loading axis are best able to resist compressive strain. Research comparing load patterns with fiber alignment in bone have tended to support Gebhardt's hypothesis. The aim of the present study is to further test this hypothesis by assessing the correspondence between the distribution of strain and the distribution of collagen fiber orientation in a bone that is subjected to compound loading (i.e., both tension and compression at different phases during the loading cycle). The ovine calcaneum was selected to meet this criterion. METHODS: Calcaneum surface strain distributions were obtained from experimental results reported by Lanyon (1973. J. Biomech. 6:41-49). Histological sections of the calcaneal shaft were prepared and observed using circularly polarized light (CPL) microscopy to determine the distribution of collagen fiber alignment. The observed alignment pattern was then compared with the predicted pattern based on Gebhardt's hypothesis. RESULTS: Contrary to previous studies, our findings show no clear correspondence between the strain type of greatest magnitude and the direction of collagen fibers. Areas of bone characterized by high compression and low tension showed predominantly longitudinal collagen alignment (contra to Gebhardt). CONCLUSIONS: It is argued that even small magnitudes of tension operating on local areas of bone may be sufficient to induce collagen alignment favorable to this type of strain, even when greater magnitudes of compressive strain are acting on the same bone volume.

Animals↗
PubMed1993

Oldest Homo and Pliocene biogeography of the Malawi Rift.

The Malawi Rift and Pliocene palaeofaunas, which include a hominid mandible attributed to Homo rudolfensis, provide a biogeographical link between the better known Plio-Pleistocene faunal records of East and Southern Africa. The Malawi Rift is in a latitudinal position suitable for recording any hominid and faunal dispersion towards the Equator that was brought on by increased aridity of the Late Pliocene African landscape. The evidence suggests that Pliocene hominids originated in the eastern African tropical domain and dispersed to southern Africa only during more favourable ecological circumstances.

Africa, Eastern↗
PubMed1991

A study of facial growth in the sooty mangabey Cercocebus atys.

This study examines the pattern of facial bone growth remodelling in the sooty mangabey (Cercocebus atys) by scanning electron microscopy (SEM) of high-accuracy replicas. The efficacy of the technique is appraised by SEM interpretations of facial remodelling in the crab-eating macaque (Macaca fascicularis) and correlative histological examination. The results indicate that the distribution of depository and resorptive areas in Cercocebus closely parallels that which has been observed in Macaca. It is suggested that the different adult facial morphologies in the sooty mangabey and crab-eating macaque are the result of changes in the rates of remodelling events that may be coupled with different patterns of sutural growth (which could not be studied by SEM).

Animals↗
PubMed1990

Regional distribution of mineral and matrix in the femurs of rats flown on Cosmos 1887 biosatellite.

We combined biochemical measurements with novel techniques for image analysis in the rat femur to characterize the location and nature of the defect in mineralization known to occur in growing animals after spaceflight. Concentrations of mineral and osteocalcin were low in the distal half of the diaphysis and concentrations of collagen were low with evidence of increased synthesis in the proximal half of the diaphysis of the flight bones. X-ray microtomography provided semiquantitative data in computer-generated sections of whole wet bone that indicated a longitudinal gradient of decreasing mineralization toward the distal diaphysis, similar to the chemistry results. Analysis of embedded sections by backscattered electrons in a scanning electron microscope revealed distinct patterns of mineral distribution in the proximal, central, and distal regions of the diaphysis and also showed a net reduction in mineral levels toward the distal shaft. Increases in mineral density to higher fractions in controls were less in the flight bones at all three levels, with the most distal cross-sectional area most affected. The combined results from these novel techniques identified the areas of femoral diaphysis most vulnerable to the mineralization defect associated with spaceflight and/or the stress of landing.

Animals↗
PubMed1987

The scanning electron microscopy/replica technique and recent applications to the study of fossil bone.

The SEM/replica technique employs high resolution replica materials in order to reflect microstructural details of specimens, such as fossil bones, which cannot be observed directly. The described technique is simple, provides excellent resolution, is maximally adaptable to field and laboratory settings, and is applicable to large and topographically complex bone surfaces. The advent of the technique has made it largely possible to address certain issues in anthropology and paleontology. These contributions have principally been concerned with taphonomy as the study of the bone damage process, and bone biology as it relates to bone growth remodeling processes characterizing the facial growth of our early fossil hominid ancestors.

Animals↗
PubMed1986

Age at death of the Neanderthal child from Devil's Tower, Gibraltar and the implications for studies of general growth and development in Neanderthals.

This study combines traditional methods of assessing dental developmental status based upon modern human standards with new techniques based upon histological observations in order to reassess the age at death of the Gibraltar child from Devil's Tower. The results indicate that the most likely age of this individual at death was 3 years of age. This result is in agreement with an independent assessment of the age of the temporal bone of this specimen (Tillier, AM [1982] Z. Morphol. Anthropol. 73:125-148) and is concordant with dental developmental ages given for modern humans. Moreover, the fact that this specimen appears at the low end of the age scale for calcification stages in modern humans is also supportive of the findings of Legoux (Legoux, P [1970] Arch. Inst. Paleontol. Hum. Mem. 33:53-87) and Wolpoff (Wolpoff, MH [1979] Am. J. Phys. Anthropol. 50:67-114) that dental eruption schedules in Neanderthals were also accelerated. If the cranial bones from Devil's Tower are associated with the dental material, as we believe, they indicate a remarkably precocious brain growth in this individual, which is consistent with what is known about general growth and development in Neanderthals.

Age Determination by Teeth↗
PubMed1985

Systematic inquiry in tests of negative/positive replica combinations for SEM.

High resolution replica materials are routinely used in scanning electron microscopy. A systematic evaluating procedure for replica combinations is proposed which details fourteen points to be recorded. These points include quantitative and qualitative information useful when assessing a replica combination for a particular research problem. A case study employing one silicone-based impression material and one epoxy resin is performed as an example of the procedure.

Animals↗
PubMed1984

Interpretation of scanning electron microscopic images of abraded forming bone surfaces.

The experimental abrasion of forming bone surfaces was conducted so that such surfaces could be characterized. This is particularly important to bone remodeling studies utilizing scanning electron microscope (SEM) imaging of archeological material. Forming surfaces derived from subadult macaque cranial bone were treated by particle abrasion, water abrasion, sliding abrasion, brushing, manual rubbing, weight, exfoliation, chipping and replication. Acetic acid treatments were also performed. The effects of abrasive agents are specific but generally fall into rough (particle and water abrasion) and smooth (sliding abrasion, brushing, rubbing and weight) categories. Protohistoric human and Plio-Pleistocene hominid subadult craniofacial remains were observed with the SEM for comparison with experimental data. The more recent material appeared smooth, probably as a result of specimen preparation procedures using brushes. Surfaces were still interpretable as forming, however, using a more abrasion-resistant feature called intervascular ridging (IVR) described in this study. The IVR pattern is also recognized on the hominid sample, confirming the possibility of performing remodeling studies on abraded fossil material. The abrasion characteristics are somewhat more difficult to classify, however. Abrasion is defined and discussed relative to remodeling studies and taphonomy. The usefulness of the experimental data reported here, however, in paleoenvironmental reconstruction, has yet to be fully realized. Acid and mechanical preparation techniques are briefly addressed. It is concluded that it is possible to characterize a forming surface as abraded according to the findings of this study and that acid, if handled with care, will more likely preserve microanatomical surface detail. It would also be in everyone's interest to employ a less abrasive cleaning regime on archeological specimens.

Animals↗
PubMed1984

Microscopic criteria for the determination of directionality of cutmarks on bone.

Shipman and Rose (1983) have recently attracted attention to the fact that the determination of directionality of cutmarks could possibly provide additional evidence for interpretation of early hominid butchering practices and handedness. They found no criteria of directionality, however. We have previously recognized directionality in cut dental tissues and more recently in bone, and so we undertook a study of over 200 experimentally produced cutmarks on bovine bone by scanning electron microscopy. Three criteria of directionality were observed: bone smears, oblique faulting, and oblique chipping. In our analysis we considered properties of bone as a relevant variable in the microscopic appearance of cutmarks, which has also led to the new finding that not all marks made by a single tool under similar conditions are the same. We observed that bone smears occurred in most specimens, relatively low density forming bone surfaces facilitated oblique fault production, whereas oblique chipping frequently occurred in plexiform bone tissue common to growing artiodactyls. In this study, handedness of the operator could be determined from cutmarks, but much further experimental work will be required in order to detail the criteria.

Animals↗
PubMed1982

Mapping remodeling reversals with the aid of the scanning electron microscope.

The histologic research on craniofacial remodeling is briefly summarized. A new methodologic approach using the scanning electron microscope (SEM) and high-resolution replicas of craniofacial bone is evaluated. Two maxillae were chosen for illustrative purposes. The specimens were replicated and prepared for routine SEM examination. In addition, a grid was applied to the replicas so that the bone growth activity states could be mapped on a coordinate system. The topographic ("T") principle is introduced as a precedent for discriminating remodeling bone growth activity states with the SEM. These activity states in vivo specify characteristic microscopic surface topographies. The three distinctive surfaces are resorptive, depository, and resting, which are mapped on a coordinate system. Results obtained are similar to those of histologic studies. The primary advantage of the SEM/replica technique is that it does not damage the specimen. This feature will facilitate more extensive investigations of craniofacial remodeling. The time and financial investments for the SEM/replica technique are significantly less than the histologic technique in the investigation of similar material. The SEM/replica technique, however, cannot be used to study nonexternal surfaces and evidence of remodeling contained within the bone cortex.

Bone Resorption↗
PubMed1982

The scanning electron microscope in craniofacial remodeling research: application of the topographic principle.

Growth and development studies utilizing craniofacial skeletal material are best done by documenting evidence of the bone growth mechanisms responsible for morphogenesis. One primary mechanism is remodeling which involves coordinated bone resorption and deposition in localized areas. Some histological studies have been performed on human facial remodeling, but these studies have been limited in extent because of the destructive nature of the technique. For obvious reasons, large skeletal research collections cannot be utilized in histological work. A new technique is presented which does not damage specimens. This involves making high resolution replicas of subadult craniofacial bone which are then examined with the scanning electron microscope (SEM) for evidence of the characteristic microscopic surface topography of remodeling bone. The Topographic ("T") principle is introduced as a precedent for discriminating remodeling bone activity states with the SEM. These activity states in vivo specify characteristic microscopic surface topographies. The three distinctive surfaces are resorptive, depository, and resting. These surfaces can be mapped on a coordinate representation of the bone replica to obtain results which are similar to those of histological studies. Application of the "T" principle and SEM/replica methodological approach offers great promise to the study of craniofacial morphogenesis.

Animals↗