While much work has been performed to quantify the extent of bone damage, its effects on the mechanical integrity of the tissue and its biological impact, the set of factors which gives forth to microdamage are nebulous, particularly the compositional properties local to microdamage. In this context, the current study tested the hypothesis that microcracks initiate within more mineralized regions of bone. Cortical bone specimens were taken from human male donors aged 31, 38, 53, 64, 71, and 84 years at the mid femoral diaphysis in a plane parallel to the osteonal orientation. The mineralization was assessed in a spatially resolved manner using Raman microspectroscopy. Arrays of measurements were taken over the entire area (i.e. global scans) of each sample followed by measurements in the vicinity of microcracks (i.e. local scans). Histograms of mineralization were constructed for global and local scans to determine whether the mineralization of damaged loci differed from the mean overall mineralization. Statistical analysis of this data revealed that the mean mineralization of damaged loci was significantly greater (P < 0.05) than the overall mineralization for each donor, indicating that there exists a highly-mineralized 'brittle volume' in bone. The presence of this damage prone 'brittle volume' has future implications for the assessment of fracture susceptibility.
Microdamage of healthy bone leads to targeted removal and repair of the damage. This process must involve the production of specific targeting signals. The identity of these signals is unknown but constitutes a legitimate research goal since it is this targeting process which appears to become impaired in ageing and disease. Here we discuss the potential role of the matrix bound osteocyte in the sensing and targeting of microdamage. In particular we will review current understanding concerning the apoptotic death of osteocytes at sites of microdamage and discuss the potential physiological significance of these findings in the light of knowledge of the significance of apoptosis in other cell systems.
The middle meningeal vascular network leaves its traces on the endocranial surface because of the tight relationship between neurocranial development and brain growth. Analysing the endocast of fossil specimens, it is therefore possible to describe the morphology of these structures, leading inferences on the cerebral physiology and metabolism in extinct human groups. In this paper, general features of the meningeal vascular traces are described for specimens included in the Homo erectus, Homo neanderthalensis, and Homo sapiens hypodigms. The complexity of the arterial network is quantified by its fractal dimension, calculated through the box-counting method. Modern humans show significant differences from the other two taxa because of the anterior vascular dominance and the larger fractal dimension. Neither the fractal dimension nor the anterior development are merely associated with cranial size increase. Considering the differences between Neanderthals and modern humans, these results may be interpreted in terms of phylogeny, cerebral functions, or cranial structural network.
Because many osteoporotic fractures occur during a fall, understanding the effect of off-axis loads on initiation and propagation of microdamage in trabecular bone should provide further insight into the biomechanics of age-related fractures. Fourteen on-axis cylindrical specimens were prepared from 12 bovine tibiae. Fluorescent stains were used to label the microdamage due to a sequence of compressive and torsional damaging loads. The mean decrease in Young's modulus was over four times greater than that in the shear modulus after the compressive overload, while there was no difference between the decrease in the axial and torsional stiffnesses after the torsional overload. The total microcrack density due to compression was uniform across the radius of the cylindrical specimens, while the mean density of microcracks due to torsional overloading increased from the axis of the cylindrical specimen to the circumference. The high density of microcracks near the axis of the specimen following torsional overloading was unexpected because of the low strains. Nearly 40% of the microcracks due to torsion propagated from pre-existing microcracks caused by axial compression, indicating that existing microcracks may extend at relatively low strain if the loading mode changes. The propagating microcracks were, on average, longer than the initiating microcracks due to either compressive or torsional loading. Damage due to axial compression appears to increase the susceptibility of trabecular bone to damage propagation during subsequent torsional loads, but it has little effect on the elastic properties in shear.
There are significant problems in obtaining normal human material for histology for teaching or research purposes. This study shows that tissue from cadavers embalmed for teaching can be used for routine histology. Twelve cadavers embalmed with four different formalin-containing embalming fluids were used (n = 3 per fluid): (1) formalin mix (10% formalin); (2) Dunedin mix (an alcohol-based fluid containing phenol); (3) Michigan mix (a water-based fluid); and (4) phenoxyethanol mix (an alcohol-based fluid containing phenoxyethanol). Tissue blocks of liver, heart, kidney, skin and skeletal muscle were taken from each cadaver, paraffin embedded, sectioned and stained with haematoxylin and eosin (H & E), Periodic Acid Schiff (PAS), or Mallory trichrome (Malt). Each section was assigned an overall score based on the histological quality of the cellular components of the tissue. Sections were scored from 1 to 3 (1 = poor, 2 = satisfactory, 3 = good). Satisfactory sections were obtained from all cadavers except those embalmed with the Dunedin mix. The Michigan and phenoxyethanol fluids resulted in consistently good quality sections. No significant differences in tissue morphology were observed between the different stains. The clearest morphology was observed in the skin and skeletal muscle sections, and in tissues embalmed with fluids which do not contain phenol.
The ontogenetic allometry of the lumbar region of 1913 humans (1228 females and 685 males), ranging from newborn to 21-year-old individuals, was studied by means of length, width, projected surface area and bone mineral density of the segment L2 - L4, obtained by dual X-ray absorptiometry (DXA). All these parameters were regressed to body mass and height of the individuals, considered alternatively as the independent variable. Firstly, we addressed the comparison between the results obtained on both sexes in order to elucidate whether ontogenetic differences existed. Length of the segments increased significantly faster in females than in males, independently whether the regression was made against body mass or height, while in both types of regression width scaled in males faster than in females. Regarding bone mineral density, although males increased bone mineral density faster than females, slope differences were not significant. However, y-interception was significantly higher in females than in males when bone mineral density was regressed to body mass. Results on length and width are compared with others from previous research on allometry. Finally, global results are discussed as regards the slope predictions for interspecific scaling.
The development of diagnostic methods and new surgical techniques means it is increasingly important to have accurate knowledge of the anatomy of the hepatic arterial and biliary systems, including their variations, at extrahepatic and intrahepatic levels. The aim of this study was to determine how often the biliary and arterial systems run together and branch in the same pattern. Fifty corrosion casts of the liver were used to analyse the origin and branching patterns of arteries and the confluences of bile ducts. In addition, both systems were analysed to determine the frequency of normal arrangements and variations. The congruence of the course of both systems was analysed at the porta hepatis and in the left and right hemilivers down to the segmental level. A congruent course of the arterial and the biliary systems was identified in 38% of cases at the porta hepatis, in 32% of cases in the left hemiliver and in 30% of the right hemiliver. The congruence of both systems at the porta hepatis and in the left hemiliver was identified only if both systems were normal. In the right hemiliver, however, the congruence of both systems was identified even when both systems were variable, but only in 10% of cases. The results of the study show that, on the basis of knowledge of the course and branching of one system, the other system cannot be predicted.
A high-calorie (cafeteria) diet is known to cause changes in the intestinal morphology and functioning that seem to be related to calorie overfeeding. Among the cell lineages found in the small intestine epithelium, the Paneth cell (PC) population is known to be influenced by factors related mainly to the intestinal microbiota. The role of PCs in the intestinal cell concert remains unclear, because experimental evidence suggests PC involvement in local processes other than protection against pathogens. Participation of PC in digestive mechanisms has been proposed on this basis. We have analyzed the effect of high-carbohydrate (HC) and high-fat (HF) cafeteria diets on the PC population in the small intestine of the adult rat. For 8 weeks, both HC and HF diets caused a gain in body weight, but whereas the HC-fed rats showed reduced counts of intestinal crypts per 5-mum section, the HF-fed group showed the opposite. In control rats, the number of crypts per section showed a slight tendency to decrease along the duodenum - ileum axis, whereas the number of PCs per crypt was increased towards the ileum. As a result, the number of PCs per section (calculated from these data) remained constant along the three segments of the intestine. The hypercaloric diets did not modify the general tendencies seen in the crypt and PC counts, but reduced the number of PCs per section in the duodenum by 50%. HC-fed, but not HF-fed, rats showed a similar reduction in jejunum also. These changes do not correlate particularly with any of the predictable effects of diet composition, so that a multifactorial control of PC density is proposed.
The mechanical breaking stress and strain of cobra leather, along with their mechanical anisotropies, were studied in relation to body movement. The mechanical breaking strain in the transverse direction (TD), which was perpendicular to the direction (CCD) from the caudal to the cranial end, was much larger around the dorsum, and slightly larger around the abdomen, than that in the CCD. The mechanical strain is closely related to the expansion of skin. The mechanical anisotropy of cobra leather was relatively large in the dorsum, but smaller in the abdomen. These findings indicate that it was comparatively easy for the cobra body to expand preferentially in the TD around the dorsum and also to expand roughly equally in all directions around the abdomen, whereas expansion of the dorsum in the CCD was restricted by the spinal column. These findings also suggest that the strong mechanical anisotropy in cobra leather is closely related to the motion of the skin around the waist, which accompanies movement of the body.
Human bones sustain fatigue damage in the form of in vivo microcracks as a result of the normal everyday loading activities. These microcracks appear to preferentially accumulate in certain regions of bone and most notably in interstitial bone matrix areas. These are remnants of old bone tissue left unremodelled, which show a higher than average mineral content and consequently the occurrence of microcracks has been attributed to the possible brittleness brought about by such hypermineralisation. There is a need, therefore, for information on the in situ bone matrix properties in the vicinity of such in vivo microcracks to elucidate the possible causes of their appearance. The present study examined the elastic, strain rate (viscous) and plastic properties of bone matrix in selectively targeted areas by nanoindentation and in both quasistatic and dynamic mode. The results showed that in vivo crack areas are not as stiff as some well-known extremely mineralised and brittle bone examples (bulla, rostrum); the strain rate effects of crack regions were identical to those of other regions of human bone and agreed well with values collected for human bone in the past at the macroscale; while the plasticity index of the crack regions was also not statistically different from most bone examples (including human at random, bovine, bulla and rostrum) except antler, which showed lower plasticity and thus a greater fraction of elastic recovery in indentation energy. It is difficult, therefore, to explain the susceptibility of these interstitial regions to crack in terms of the mineral content and its after-effects on elasticity, viscosity and plasticity alone, but one need to attribute the cracks to the cumulative loading history of these areas, or raise the suggestion that these areas of bone matrix are in some measure 'aged' or material/quality defective.
The cephalic and pectoral girdle structures of the pimelodin Pimelodus blochii (Pimelodus group) are described and compared to those of representatives of the two other main pimelodin groups, namely Calophysus macropterus (Calophysus group) and Pseudoplatystoma fasciatum (Sorubim group), and of a representative of the peculiar pimelodin genus Hypophthalmus, H. edentatus, and several other catfishes, as the foundation for a discussion on the synapomorphies and phylogenetic relationships of the Pimelodinae. Three new, additional potential synapomorphies to support the monophyly of the Pimelodinae are pointed out: (1) presence of a 'muscle 1 of the mandibular barbels' running from the antero-ventro-mesial surface of the cartilaginous plates carrying these barbels to the dentaries; (2) presence of a muscle tensor tripodis running from the posterior surface of the neurocranium to the dorsal surface of the swimbladder near the tripus; and (3) presence of a 'drumming muscle of the swimbladder' running from the parapophyses of the fourth vertebra and, eventually, the posterior surface of the neurocranium, to the antero and antero-ventral surface of the swimbladder. The subfamilies Pimelodinae, Heptapterinae and Pseudopimelodinae seem to constitute a monophyletic assemblage, thus contradicting the commonly accepted idea that the family Pimelodidae is a polyphyletic clade.
The distribution of complex glycoconjugates and antimicrobial substances in the ceruminous glands of the horse (Equus przewalskii f. dom., type: pony) was studied using carbohydrate histochemical and immunohistochemical methods. The epithelial cells and luminal secretion of these glands exhibited considerable amounts of glycoconjugates with various saccharide residues, such as alpha-D-mannose, alpha-L-fucose, beta-D-galactose, beta-N-acetyl-D-glucosamine and sialic acid, including O-acetylated sialic acid. Several sugars (alpha-D-mannose, alpha-L-fucose, and beta-D-galactose) were also detectable in the secretion of sebaceous glands present. Additionally, lysozyme and the peptide group of beta-defensins are demonstrated as products of the apocrine ceruminous glands and sebaceous glands. The results obtained are discussed with regard to the functional significance of the glandular secretions. It is suggested that the complex carbohydrates, lysozyme and beta-defensins found in the ceruminous gland secretions are involved in the function of cerumen as a general antimicrobial protective agent in the external auditory canal.
Mechanical forces due to increased blood flow during the first pregnancy might induce a permanently higher conductance of the uterine arcade. Number of endothelial and smooth muscle cells, cross-sectional area and wall thickness of the uterine artery were measured in nulliparous mice (n = 11) and until the 93rd day after parturition in primiparous mice (n = 44). Inner diameter and wall area were calculated. Three months after the first pregnancy, uterine artery wall thickness was not altered compared to nulliparous mice. In contrast, inner diameter increased 1.6-fold, wall area 1.5-fold and the numbers of endothelial and smooth muscle cells increased 1.5 times. These changes were completely stable during the whole observation period. The increased blood flow during the first pregnancy might be a mandatory mechanical stimulus for uterine arcade maturation. This physiological maturation process could result in abortion explaining the higher prevalence of unexplained pregnancy losses in primiparous women.
This paper summarises four separate studies carried out by our group over the past number of years in the area of bone microdamage. The first study investigated the manner by which microcracks accumulate and interact with bone microstructure during fatigue testing of compact bone specimens. In a series of fatigue tests carried out at four different stress ranges between 50 and 80 MPA, crack density increased with loading cycles at a rate determined by the applied stress. Variations in the patterns of microdamage accumulation suggest that that at low stress levels, larger amounts of damage can build up without failure occurring. In a second study using a series of four-pont bending tests carried out on ovine bone samples, it was shown that bone microstructure influenced the ability of microcracks to propagate, with secondary osteons acting as barriers to crack growth. In a third study, the manner by which crack growth disrupts the canalicular processes connecting osteocytes was investigated. Analysis of individual cracks showed that disruption of the canalicular processes connecting osteocytes occurred due to shear displacement at the face of propagating microcracks, suggesting that this may play some role in the mechanism that signals bone remodelling. In a fourth in vivo study, it was shown that altering the mechanical load applied to the long bones of growing rats causes microcrack formation. In vivo microdamage was present in rats subjected to hindlimb suspension with a higher microcrack density found in the humeri than the femora. Microdamage was also found in control animals. This is the first study to demonstrate in vivo microcracks in normally loaded bones in a rat model.
Despite a general understanding that bone quality contributes to skeletal fragility, very little information exits on the age-dependent fatigue behavior of human bone. In this study four-point bending fatigue tests were conducted on aging bone in conjunction with the analysis of stiffness loss and preliminary investigation of nanoindentation based measurements of local tissue stiffness and histological evaluation of resultant tensile and compressive damage to identify the damage mechanism responsible for the increase in age-related bone fragility. The results obtained show that there is an exponential decrease in fatigue life with age, and old bone exhibits different modulus degradation profiles than young bone. In addition, this study provides preliminary evidence indicating that during fatigue loading, younger bone formed diffuse damage, lost local tissue stiffness on the tensile side. Older bone, in contrast, formed linear microcracks lost local tissue stiffness on the compressive side. Thus, the propensity of aging human bone to form more linear microcracks than diffuse damage may be a significant contributor to bone quality, and age related fragility in bone.
The biphalangeal little toe is an anatomical anomaly that has been previously well described in the early anatomical literature. But, as is the case with many anomalies, there is a lack of awareness of it amongst current clinicians. We report the case of a fracture through the distal phalanx of the little toe, with a delay in the diagnosis due to confusion over the X-ray findings. X-rays revealed a biphalangeal toe with a fracture through the distal phalanx, which mimicked the usual triphalangeal toe. This is the first reported case of clinical confusion over this anatomical variation. A review of 102 human skeletal feet at the Department of Anatomy, University of Melbourne, was performed to evaluate the frequency of the biphalangeal little toe variant, revealing an incidence of 26%.
Bone remodelling has been associated with microdamage. The aim of this study was to investigate the presence of microdamage in the alveolar bone and its potential role in the initiation of bone remodelling following the application of an orthodontic load. The three-dimensional morphology of the alveolar bone was investigated by means of high resolution micro-CT scanning. In 25, 3-month-old, male Danish land-race pigs, the alveolar bone around the lower right and left first molars was analysed. The right first molar was moved buccally with a force of 130 cN by means of a custom-made cantilever made of a TMA 0.017 x 0.025 inch wire. The left molar was left untreated. After 1, 2, 4, 7 and 15 days of treatment the regions containing the right and left molars were excised and en bloc stained in basic fuchsin and the presence of microdamage detected. Diffuse damage was present in the alveolar bone of both the treated and the untreated teeth on both sides. On the lingual sides, diffuse damage showed the same orientation as the periodontal fibres. Bone microcracks were also detected on both the treated and untreated teeth. On the buccal surfaces they where often observed in close proximity to scalloped resorption surfaces. After 1 day of treatment, the presence of microcracks on the buccal-treated side was particularly marked. To conclude, bone microdamage is present in porcine alveolar bone in form of both microcracks and diffuse damage, suggesting that microdamage-driven remodelling also occurs in the alveolar bone. The presence of bone microcracks in the direction of the orthodontic force at day 1 suggests that they could represent the first damage induced by the orthodontic load that has to be repaired.
This study aimed to describe the impressive diversity of vascular plexiform structures of the hypodermal layer of human skin. We chose the human body site with the highest concentration of dermal corpuscles, the human digit, and processed it with the corrosion casting technique and scanning electron microscopy analysis (SEM). This approach proved to be the best tool to study these microvascular architectures, free from any interference by surrounding tissues. We took high-definition pictures of the vascular network of sweat glands, thermoreceptorial and tactile corpuscles, the vessels constituting the glomic bodies and those feeding the hair follicles. We observed that the three-dimensional disposition of these vessels strictly depends on the shape of the corpuscles supplied. We could see the tubular vascularization of the excretory duct of sweat glands and the ovoid one feeding their bodies, sometimes made up of two lobes. In some cases, knowledge of these morphological data regarding the normal disposition in space and intrinsic vascularization structure of the dermal corpuscles can help to explain many of the physiopathological changes occurring during chronic microangiopathic diseases.
