Bone vascular supply in monitor lizards (Squamata: Varanidae): influence of size, growth, and phylogeny

Bone vascular canals occur irregularly in tetrapods; however, the reason why a species has or lacks bone canals remains poorly understood. Basically, this feature could depend on phylogenetic history, or result from diverse causes, especially cortical accretion rate. The Varanidae, a monophyletic clade that includes species with impressive size differences but similar morphologies, is an excellent model for this question. Cortical vascularization was studied in 20 monitor species, on three bones (femur, fibula, and tibia) that differ in their shaft diameters, and in the absolute growth speed of their diaphyseal cortices. In all species smaller than 398 mm SVL (133-397 mm in sample), bone cortices lack vascular canals, whereas all larger species (460-1,170 mm in sample) display canals. The size 398-460 mm SVL is thus a threshold for the appearance of the canals. The distribution of vascular and avascular bone tissues among species does not precisely reflect phylogenetic relationships. When present, vascular canals always occur in the femur and tibia, but are less frequent, sparser, and thinner in the fibula. Vascular density increases linearly with specific size but decreases exponentially during individual growth. In most species, canal orientation varies between individuals and is diverse in a single section. No clear relationship exists between canal orientation and vascular density. These results suggest that: a) the occurrence and density of bone vascular canals are basically dependant on specific size, not phylogenetic relationships; b) vascular density reflects the absolute growth rates of bone cortices; c) the orientation of vascular canals is a variable feature independent of phylogeny or growth rate.     

Formation of actin filament bundles in the ring canals of developing Drosophila follicles

Growing the intracellular bridges that connect nurse cells with each o ther and to the developing oocyte is vital for egg development. These ring canals increase from 0.5 microns in diameter at stage 2 to 10 microns in diameter at stage 11. Thin sections cut horizontally as you would cut a bagel, show that there is a layer of circumferentially oriented actin filaments attached to the plasma membrane at the periphery of each canal. By decoration with subfragment 1 of myosin we find actin filaments of mixed polarities in the ring such as found in the "contractile ring" formed during cytokinesis. In vertical sections through the canal the actin filaments appear as dense dots. At stage 2 there are 82 actin filaments in the ring, by stage 6 there are 717 and by stage 10 there are 726. Taking into account the diameter, this indicates that there is 170 microns of actin filaments/canal at stage 2 (pi x 0.5 microns x 82), 14,000 microns at stage 9 and approximately 23,000 microns at stage 11 or one inch of actin filament! The density of actin filaments remains unchanged throughout development. What is particularly striking is that by stages 4-5, the ring of actin filaments has achieved its maximum thickness, even though the diameter has not yet increased significantly. Thereafter, the diameter increases. Throughout development, stages 2-11, the canal length also increases. Although the density (number of actin filaments/micron2) through a canal remains constant from stage 5 on, the actin filaments appear as a net of interconnected bundles. Further information on this net of bundles comes from studying mutant animals that lack kelch, a protein located in the ring canal that has homology to the actin binding protein, scruin. In this mutant, the actin filaments form normally but individual bundles that comprise the fibers of the net are not bound tightly together. Some bundles enter into the ring canal lumen but do not completely occlude the lumen. all these observations lay the groundwork for our understanding of how a noncontractile ring increases in thickness, diameter, and length during development.     

Effects of Externally Applied Pressure on the Haemodynamics of the Lower Limb

The effects of externally applied pressure of 5-150 mm Hg on the haemodynamics of the leg of dog and man were investigated. The criteria used for the assessments included femoral arterial and venous blood flow as well as vascular hydraulic conductance. The results indicated that external pressure of 5 mm Hg results in a very small non-significant increase in the femoral arterial and venous flow. Higher external pressure of 15 mm Hg or more significantly reduces the femoral arterial and venous flows as well as the vascular conductance. It therefore seems that compression produced by bandaging in horizontal supine subjects has little or no haemodynamic value and may prove to be harmful unless carefully controlled.     

两种根管冲洗液对狗牙根管内细菌抗菌作用的实验研究

目的观察2%洗必泰溶液和3%双氧水2种根管冲洗液对狗牙根管内粪肠球菌、溶血链球菌、微小消化链球菌、中间普氏菌及具核酸杆菌的影响,为临床根管治疗提供参考。方法选择成年健康杂种狗3只,共有24个实验牙,48个实验牙根。于狗牙根管内接种粪肠球菌、溶血链球菌、微小消化链球菌、中间普氏菌及具核酸杆菌。对狗牙完成根管治疗。于治疗后12个月拍摄根尖X线片,并记录牙齿和根尖周组织的临床表现。将患牙随机分为3组,每组7颗患牙,去除根管内充填物并进行根管预备,实验一组用2%洗必泰溶液冲洗根管,实验二组用3%双氧水冲洗根管,对照组用0.9%NaC l溶液冲洗根管。分别在根管预备前及根管预备冲洗后对根管内细菌取样,培养,鉴定并记录细菌菌落数量,测定根管内细菌变化情况。结果根管预备冲洗后3组根管内的细菌量均较根管预备前显著下降（P〈0.05）。2%洗必泰溶液和3%双氧水2种根管冲洗液的杀菌效果明显好于0.9%NaC l溶液（P〈0.05）,2%洗必泰溶液明显好于3%双氧水（P〈0.05）。结论2%洗必泰溶液是有效的根管冲洗药物,可明显减少狗牙根管内粪肠球菌、溶血链球菌、微小消化链球菌、中间普氏菌及具核酸杆菌的数量,但不能完全清除根管内的细菌。     

The system of bony canals as the basis for the angioarchitectonics of bones]

The spatial interrelationships of osteon canals were studied in corrosion preparations with the help of rastral electron microscopy. The structure of microvessels, their belonging to a definite link of the microcirculatory bed, the interaction of vessels and their position with respect to the osseous matrix were studied in bone sections impregnated with silver nitrate after V. V. Kuprijanov. Haversian canals in the compact substance of the bone are longitudinally oriented, can duplicate and form a single system of canals. The neighbouring canals of osteons might be bound by means of Volkmann's canals. The investigation of the Haversian canals in serial sections has shown that the diameter of the same canals of osteons can change at different levels, the diameter of the osteons themselves remaining unchanged. This seems to speak of uneven development of osteons in their different parts. In the Haversian canal there are one-two or occasionally three vessels having all three links of the morphocirculatory bed. The course and ramification of the vessel are identical to the shape of the osteon canal which includes them. The vessels are closely connected with the bony matrix by means of connective tissue bundles directed from the canal wall to the vessel wall. These bundles appear to serve as a peculiar anchor or amortizing apparatus and its elasticity might be a factor of a change of the shape and direction of the canal vessels in the bone development process.     

Animal welfare in modern dog breeding

Background

While gross morphological changes in the skeleton between males and females are well know, differences between sexes in the histomorphology are less known. It is important to have knowledge on the bone structure of rabbits, as this is a widely used species in biomedical research. A study was performed to evaluate the association between sex and the compact bone morphology of the femoral diaphysis in juvenile rabbits.

Methods

Seventeen clinically healthy 2–3 month-old rabbits (9 females, 8 males) were included in the study. The rabbits were euthanized and the right femur was sampled for analysis. 70–80 microns thick bone sections of the femoral diaphysis were prepared using standard histological equipment. The qualitative histological characteristics were determined according to internationally accepted classification systems while the quantitative parameters were assessed using the software Scion Image. Areas, perimeters, minimum and maximum diameters of primary osteons' vascular canals, Haversian canals and secondary osteons were measured. Additionally, blood plasma concentrations of progesterone, corticosterone, IGF-I, testosterone and estradiol were analyzed.

Results

Qualitative histological characteristics were similar for both sexes. However, variations of certain quantitative histological characteristics were identified. Measured parameters of the primary osteons' vascular canals were higher in males than for females. On the other hand, females had significant higher values of secondary osteons parameters. Differences in Haversian canals parameters were only significant for minimum diameter.

Conclusion

The study demonstrated that quantitative histological characteristics of compact bone tissue of the femoral diaphysis in juvenile rabbits were sex dependent. The variations may be associated with different growth and modeling of the femur through influence by sex-specific steroids, mechanical loads, genetic factors and a multitude of other sources. The results can be applied in experimental studies focusing on comparison of the skeletal biology of the sexes.     

Experimental infection of Paragonimus iloktsuenensis to albino rats, dogs and cats

This study was performed to observe the susceptibility of dogs and cats as definitive hosts of Paragonimus iloktsuenensis. The metacercariae of this fluke were obtained from Sesarma dehaani collected at a focus near the mouth of Sumjin river in November, 1986 and February, 1987. The larvae isolated from the crabs were introduced per os into 7 albino rats, 2 dogs and 3 cats. The adults were recovered from the experimental animals, and they were morphologically observed and measured. The results were as follows: 1. The recovery rate of adult worms at 42 days after infection was 53.3% from three albino rats, 21.0% from a dog and 12.7% from two cats. Most of the worms were recovered from the worm capsules in the lungs. 2. The size of worms recovered from albino rats, a dog, and cats 42 days after infection averaged 6.3 x 3.2 mm, 6.3 x 3.0 mm, or 6.2 x 3.5 mm, respectively. There were little differences in the morphology of worms by different experimental animals. 3. The size of eggs from a dog was 88.9 x 49.3 microns, and that from cats was 84.3 x 53.7 microns on average. Dogs and cats were good definitive hosts of P. iloktsuenensis. This fact suggests that human infection by this fluke may be possible if the metacercariae were ingested.     

Some aspects of the system of Haversian canals in the diaphysary compact bone in man

The general aspect of the network of Haversian canals was studied on tangential and radial sections from the diaphysary compact bone of the human long bones. The network-like aspect was much varied even in the same bone and at the same level from which the samples were obtained. No obvious differences were found between the studied bones or between the two limbs. Certain peculiarities of the canal system were noticed as regards the trajectory of canals, disposition and number of anastomoses, and the network aspect, depending on the region of the diaphysis, but especially on the depth.     

Development of the supraorbital and mandibular lateral line canals in the cichlid,Archocentrus nigrofasciatus

The development of two of the cranial lateral line canals is described in the cichlid, Archocentrus nigrofasciatus. Four stages of canal morphogenesis are defined based on histological analysis of the supraorbital and mandibular canals. "Canal enclosure" and "canal ossification" are defined as two discrete stages in lateral line canal development, which differ in duration, an observation that has interesting implications for the ontogeny of lateral line function. Canal diameter in the vicinity of individual neuromasts begins to increase before ossification of the canal roof in each canal segment; this increase in canal diameter is accompanied by an increase in canal neuromast size. The mandibular canal generally develops later than the supraorbital canal in this species, but in both of these canals development of the different canal segments contained within a single dermal bone is asynchronous. These observations suggest that a dynamic process requiring integration and interaction among different tissues, in both space and time, underlies the development of the cranial lateral line canal system. The supraorbital and mandibular canals appear to demonstrate a "one-component" pattern of development in Archocentrus nigrofasciatus, where the walls of each canal segment grow up from the underlying dermal bone and then fuse to form the bony canal roof. This is contrary to numerous published reports that describe a "two-component" pattern of development in teleosts where the bony canal ossifies separately and then fuses with an underlying dermal bone. A survey of the literature in which lateral line canal development is described using histological analysis suggests that the occurrence of two different patterns of canal morphogenesis ("one-component" and "two-component") may be due to phylogenetic variation in the pattern of the development of the lateral line canals.     

Alterations of the resin canal system of <Emphasis Type="Italic">Pinus pinaster</Emphasis> seedlings after fertilization of a healthy and of a <Emphasis Type="Italic">Hylobius abietis</Emphasis> attacked stand

Changes in resource availability and biotic and abiotic stress may alter the defensive mechanisms of pine trees. The effect of fertilisation on the resin canal structure of Pinus pinaster seedlings established in two trials in NW Spain, one attacked by Hylobius abietis and the other non-attacked, was studied. The leaders of 50 plants were destructively sampled and the resin canal density, the canal area and its relative conductive area in the phloem and xylem were assessed. Experimentally increased nutrient availability significantly decreased resin canal density in the phloem of the seedlings in the two analysed trials, where unfertilised seedlings presented up to 30% more resin canal density than the fertilised seedlings (mean value ± SEM = 0.32 ± 0.02 resin canals mm⁻² in the fertilised plants versus 0.45 ± 0.04 resin canals mm⁻² in the control plants). Fertilisation had no effect on the resin canal system in the xylem, but significantly increased tracheid size. Significant differences of resin canals among sites were observed mainly in the xylem; the resin canal density was 1.7-fold greater in the attacked site than in the non-attacked site. The similar structure of phloem resin canals in both sites supports that phloem resin canals are constitutive mechanisms of defence in P. pinaster, whereas xylem resin canals would be constitutive mechanisms but also inducible mechanisms of resistance following the attack of pine weevils or bark beetles. XM and LS equally contributed to this paper.     

The comparative ultrastructure of the egg membrane and associated pore structures in the starry flounder,Platichthys stellatus (Pallas), and pink salmon,Oncorhynchus gorbuscha (Walbaum)

Eggs of the starry flounder (Platichthys stellatus) and pink salmon (Oncorhynchus gorbuscha) were examined by scanning and transmission electron microscopy to determine differences in egg membrane structure with reference to contrasting ecological conditions in which the eggs normally develop. The egg membrane of the starry flounder constitutes 0.22--0.50% of the egg's diameter. The zona radiata is composed of 6 continuous horizontal lamellae, covered by a thin triple layered border, and pierced by numerous regularly spaced pore canals. The micropyle canal measures 8 microns at the opening and tapers to 3.6 microns as it penetrates the membrane. In contrast, the thicker membrane of the pink salmon egg forms 0.80--1.0% of the egg's diameter, is composed of numerous short discontinuous lamellae which are pierced by pore canals, and is covered by a coating of irregular thickness. The 15--16 micron micropyle opening is surrounded by an area of protrusions, and the funnel-shaped canal tapers to 2 microns at its terminal aperture. Contrasting environmental conditions during embryogenesis of these two species may be reflected by the thin membrane and simple lamellar structure in the pelagic egg of the starry flounder, and the thick membrane and complex lamellar structure in the demersal egg of the pink salmon.     

The canine baculum: the structure and mechanical properties of an unusual bone

The baculum is an extraskeletal bone located in the penis of a few species in several orders of mammals such as carnivores, insectivores, rodents, bats and primates. This study aims to describe the structure, architecture and mechanical properties of the canine baculum. To this end canine bacula from castrated and uncastrated dogs were collected and examined by light microscopy, micro-computed tomography (microCT) scanning, histological staining, and mechanical testing. Their mineral density and mechanical properties were compared with those of a typical skeletal bone (the radius) in the same dog. Furthermore, a numerical model of a representative baculum was created and its mechanical performance analyzed using the finite element method, in order to try to elucidate its function. Examination of light microscopy images of transverse sections shows that the baculum consists of a typical sandwich structure, with two cortical plates separated, and joined, by loose cancellous bone. MicroCT scans reveal that the mineral density is lower in the baculum than in the radius, both in castrated as well as in uncastrated dogs, resulting in much lower stiffness. Castration was found to decrease the mineral density in both the baculum and the radius. The most likely function of the baculum of the dog is to stiffen the penis to assist intromission, and its much lower mineral density compared to that of the radius may be a mechanism designed to decrease the stiffness somewhat, and thus reduce the risk of fracture during copulation.     

The Sensory Canal Systems of the Living Coelacanth, Latimeria Chalumnae: A New Instalment

Entire sensory canal systems of the coelacanth, Latimeria chalumnae, are described: not only the course of principal canals with their primary and secondary collaterals, but also the course and branches of the pit-line and reticular canals. The number of pores on the left side of the head were found to be 296 in an early (yolksac) embryo, 321 in a late term fetus, 485 in a juvenile, and 2974 in adults. This means that in latimeria most of the lateral-line canal system develop after parturition. Pit lines of the living coelacanth are not rows of superficial neuromasts but canals covered by a thin epidermis like in other sensory canals of the lateral line. These pit-line canals, however, have a very specific structure and branching pattern: the medial dorsal pit-line canal is connected by fine branches on top of the head. The infra-dentary pit-line canal connects via these branches with canals deep inside the bones. Several fine and richly branched canaliculi of unknown function radiate from each quadratojugal pit-line canal. The gular plate pit-line canal has superficially branching arms as well as connections to numerous deeper canals inside the bone. These canals consist of fine branches that in turn lead to and open on the ventral surface of the gular plates as small pores. The system is reminiscent of the reticular (pore) canal system known only from some fossil agnathans and fishes. Thus latimeria combines the reticular system of ancient vertebrates with the lateral-line system of modern fishes. The significance of this gular (possibly electro-sensory) system for feeding by the coelacanth will be discussed.     

Evaluation of Dog Bones in the Indirect Assessment of Environmental Contamination with Trace Elements

The aim of this paper was to determine the level of five elements, two essential for life [zinc (Zn) and copper (Cu)] and three distinctly toxic [lead (Pb), cadmium (Cd), and mercury (Hg)], in four types of biological material in bones of the dog Canis lupus familiaris. The experiment was carried out on bones from the hip joints of dogs. The samples of cartilage, compact bone, spongy bone, and cartilage with adjacent compact bone came from 26 domestic dogs from northwestern Poland. Concentrations of Cu, Zn, Pb, and Cd were determined by ICP-AES (atomic absorption spectrophotometry) in inductively coupled argon plasma, using a Perkin-Elmer Optima 2000 DV. Determination of Hg concentration was performed by atomic absorption spectroscopy. In the examined bone material from the dog, the greatest concentrations (median) were observed for Zn and the lowest for Hg (98 mg Zn/kg and 0.0015 mg Hg/kg dw, respectively). In cartilage and spongy bone, metal concentrations could be arranged in the following descending order: Zn > Pb > Cu > Cd > Hg. In compact bone, the order was slightly different: Zn > Pb > Cd > Cu > Hg (from median 70 mg/kg dw to 0.002 mg/kg dw). The comparisons of metal concentrations between the examined bone materials showed distinct differences only in relation to Hg: between concentrations in spongy bone, compact bone, and in cartilage, being greater in cartilage than in compact bone, and lower again in spongy bone.     

Occlusion pressures vs. micropipette pressures in the pulmonary circulation

Because of the discrepancies between the arterial and venous occlusion technique and the micropuncture technique in estimating pulmonary capillary pressure gradient, we compared measurements made with the two techniques in the same preparations (isolated left lower lobe of dog lung). In addition, we also obtained direct and reliable measurements of pressures in 0.9-mm arteries and veins using a retrograde catheterization technique, as well as a microvascular pressure made with the double-occlusion technique. The following conclusions were made from dog lobes perfused with autologous blood at normal flow rate of 500-600 ml/min and pressure gradient of 12 mmHg. 1) The double-occlusion technique measures pressure in the capillaries, 2) a small pressure gradient (0.5 mmHg) exists between 30- to 50-micron arteries and veins, 3) a large pressure gradient occurs in arteries and veins greater than 0.9 mm, 4) the arterial and venous occlusion techniques measure pressures in vessels that are less than 900 microns diam but greater than 50 microns, very likely close to 100 microns, 5) serotonin constricts arteries (larger and smaller than 0.9 mm) whereas histamine constricts veins (larger and smaller than 0.9 mm). Thus three different techniques (small retrograde catheter, arterial and venous occlusion, and micropuncture) show consistent results, confirming the presence of significant resistance in large arteries and veins with minimal resistance in the microcirculation.     

Morphometric variations of the lumbar vertebrae between Chinese and Indian adults.

A morphometric study of the lumbar vertebrae of 126 adult skeletons, 90 Chinese and 36 Indian, of both sexes without marginal osteophytes were performed. In each lumbar vertebra, the cephalad and caudad midsagittal diameters, the interpedicular diameter of the spinal canal as well as the midsagittal and transverse diameters and the height of the vertebral body were measured. The results showed that the midsagittal and transverse diameters, the heights of the lumbar vertebral bodies and the interpedicular diameters of the lumbar spinal canals increased progressively from L1 to L5, while the midsagittal diameters of the lumbar spinal canals decreased progressively from L1 to L5 in both Chinese and Indian adult skeletons. The lowest mean values of the cephalad and caudad midsagittal and the interpedicular diameters of the spinal canals in Chinese were found to be 5.04 +/- 0.15 mm at L5, 4.67 +/- 0.09 mm at L5 and 25.92 +/- 0.20 mm at L2, respectively, while in Indians they were found to be 4.54 +/- 0.18 mm at L5, 4.25 +/- 0.10 mm at L5 and 25.42 +/- 0.22 mm at L1, respectively. In addition, the mean diameters of the spinal canal and the vertebral body (except the height of the vertebral body) were significantly greater in the Chinese than in the Indian skeletons. The above findings indicate that the mean diameters of both the lumbar spinal canal and the vertebral body vary greatly between Chinese and Indian adults, i.e. there are no mean values of the vertebral dimensions that are valid for all populations.(ABSTRACT TRUNCATED AT 250 WORDS)     

Increased intracortical bone remodeling during lactation in beagle dogs

There are substantial changes in skeletal and mineral metabolism during pregnancy and lactation. The purpose of this study was to determine the changes in intracortical bone remodeling and turnover during lactation in beagle dogs. A femur and rib were obtained from dogs near the end of lactation or soon after weaning and compared with nonlactating controls. Rib cortical bone had much higher bone turnover rates than did femoral diaphyseal cortical bone. The number of single-labeled osteons and the number of resorption spaces were significantly greater during lactation in both the rib and the femur. Additionally, the mineral apposition rate, basic multicellular unit activation frequency, and bone turnover rates were greater in the femoral cortical bone from the lactating dogs than from the controls. These data demonstrate that during lactation, intracortical bone remodeling increases, and this may provide a mechanism for the skeleton to be responsive to the calcium requirements of the mother. In addition, these data may help explain the transient decreases in cortical bone mineral density that are reported to occur during human lactation.     

Group conduction velocities and nerve fibre diameters of alpha and gamma-motoneurons from lower sacral nerve roots of the dog and humans.

Single action potentials and their conduction times were recorded extracellularly from dog and human lower sacral nerve roots. Conduction velocity frequency distribution histograms were constructed and peaks of single extrafusal and intrafusal motoneuron distributions were identified. The electrophysiologically measured roots were removed and morphometrically analysed. Nerve fibre diameter frequency distribution histograms were constructed with respect to 3 myelin sheath thickness ranges, and peaks of single motoneuron group distributions were identified. The identified motoneuron classes, characterized by their group peak values of conduction velocity at about 36 degrees C and fibre diameter were: dog: intrafusal: gamma 22(23ms-1/4.8 microns),gamma 21(33/5.7), gamma 1 (43/6.7),gamma beta?(54/10.1) extrafusal: alpha 3(61ms-1/11.7 microns),alpha 2(72/13.6), alpha 11 (81/15.2), alpha 12(86/16.8),alpha 13(95/19) human: intrafusal: gamma 21(15ms-1/5.8 microns), gamma 1(20/6.8), gamma beta?(27/7.2) extrafusal: alpha 3(37ms-1/8.3 microns),alpha 2(50/10.2), alpha 1(60/13.1) The 60 (alpha 3) to 30% (alpha 1-motoneurons) higher conduction velocities in dogs as compared to humans seem to originate in the 40 (alpha 3) to 30% (alpha 1-motoneurons) larger nerve fibre diameters. However, the myelin sheath seemed to be 0.1 to 0.2 microns thinner in dogs than in humans. The pair-values "conduction velocity-fibre diameter" of the alpha and gamma-motoneuron groups were lying on different correlation curves in the velocity-diameter plane indicating structural and/or geometrical differences between alpha and gamma-motoneurons.     

Selection of an animal model for implant fixation studies: anatomical aspects.

A number of different animal models have been employed by investigators to study the biology of the bone-cement interface as it relates to the problem of hip implant loosening in humans. This study compares to the human three species (baboon, dog, and sheep) currently under use as experimental animal models from an anatomical point of view. A number of parameters, important for the dimensional design of a femoral prosthesis, loads at the hip joint and its subsequent performance, were used for comparing external and internal femoral anatomy. The baboon and dog femora were found to be most similar to the human femur in their external anatomy. The quantification of cancellous bone distribution within the medullary canal revealed that, of the species studied, the sheep femur provided the least support to the prosthesis. The results suggest that the dog and baboon are anatomically appropriate for studying hip implant biomechanics experimentally. Thus, from an anatomical point of view, the current extensive use of the dog as an experimental animal appears appropriate.     

Patterns of femoral bone remodeling dynamics in a medieval Nubian population

The relationship between age, sex and histomorphometry in femoral cortical bone was examined in a skeletal population of late Medieval antiquity (AD 1250–1450) from Kulubnarti, in Sudanese Nubia. These skeletal remains are naturally mummified and in an excellent state of preservation. The study sample consisted of femoral cross sections from 24 females and 19 males ranging in age from 20 to 50+ years. Femoral cross sections were examined using an image analysis system. Numbers of secondary osteons and osteon fragments were counted, osteon area and Haversian canal area were measured, and several variables were calculated to assess differences between sexes and among age groups in bone remodeling variables. The results indicate significant differences between the sexes in osteon number and size. Males had significantly more intact osteons than females, whereas females had significantly larger osteons than males. Haversian canal dimensions were not statistically significant between the sexes. Sex differences in activity patterns in which males were involved in more physically strenuous tasks may have contributed to differences in remodeling variables. Interpopulational comparisons suggest that mechanical strain affects the microstructural features examined in this study. In particular, small Haversian canals in some archaeological skeletal populations are associated with higher bone volume, which may result from high levels of mechanical strain. Am J Phys Anthropol 104:133–146, 1997. © 1997 Wiley-Liss, Inc.