Secondary Trabeculae Research Articles

Differential osteoblastic activity in primary metaphyseal trabecular and secondary trabeculae of c-fos deficient mice

ObjectivesIt has been highlighted that osteoblastic activities in remodeling-based bone formation are coupled with osteoclastic bone resorption while those in modeling-based bone formation are independent of osteoclasts. This study aimed to verify whether modeling-based bone formation can occur in the absence of osteoclasts. MethodsWe performed histochemical analyses on the bone of eight-week-old male wild-type and c-fos−/− mice. Histochemical analyses were conducted on primary trabeculae near the chondro-osseous junction (COJ), sites of modeling-based bone formation, and secondary trabeculae, sites of remodeling-based bone formation, in the femora and tibiae of mice. ResultsAlkaline phosphatase (ALP) immunoreactivity, a marker of osteoblastic lineages, was observed in the metaphyseal trabeculae of wild-type mice, while ALP was scattered throughout the femora of c-fos−/− mice. PHOSPHO1, an enzyme involved in matrix vesicle-mediated mineralization, was predominantly detected in primary trabeculae and also within short lines of osteoblasts in secondary trabeculae of wild-type mice. In contrast, femora of c-fos−/− mice showed several patches of PHOSPHO1 positivity in the primary trabeculae, but there were hardly any patches of PHOSPHO1 in secondary trabeculae. Calcein labeling was consistently observed in primary trabeculae close to the COJ in both wild-type and c-fos−/− mice; however, calcein labeling in the secondary trabeculae was only detected in wild-type mice. Transmission electron microscopic examination demonstrated abundant rough endoplasmic reticulum in the osteoblasts in secondary trabeculae of wild-type mice, but not in those of c-fos−/− mice. ConclusionsOsteoblastic activities at the sites of modeling-based bone formation may be maintained in the absence of osteoclasts.

Comparative bone histology of two thalattosaurians (Diapsida: Thalattosauria): Askeptosaurus italicus from the Alpine Triassic (Middle Triassic) and a Thalattosauroidea indet. from the Carnian of Oregon (Late Triassic)

Here, we present the first bone histological and microanatomical study of thalattosaurians, an enigmatic group among Triassic marine reptiles. Two taxa of thalattosaurians, the askeptosauroid Askeptosaurus italicus and one as yet undescribed thalattosauroid, are examined. Both taxa have a rather different microanatomy, tissue type, and growth pattern. Askeptosaurus italicus from the late Anisian middle Besano Formation of the southern Alpine Triassic shows very compact tissue in vertebrae, rib, a gastralium, and femora, and all bones are without medullary cavities. The tissue shows moderate to low vascularization, dominated by highly organized and very coarse parallel-fibred bone, resembling interwoven tissue. Vascularization is dominated by simple longitudinal vascular canals, except for the larger femur of Askeptosaurus, where simple vascular canals dominate in a radial arrangement. Growth marks stratify the cortex of femora. The vertebrae and humeri from the undescribed thalattosauroid from the late Carnian of Oregon have primary and secondary cancellous bone, resulting in an overall low bone compactness. Two dorsal vertebral centra show dominantly secondary trabeculae, whereas a caudal vertebral centrum shows much primary trabecular bone, globuli ossei, and cartilage, indicating an earlier ontogenetic stage of the specimens or paedomorphosis. The humeri of the thalattosauroid show large, simple vascular canals that are dominantly radially oriented in a scaffold of woven and loosely organized parallel-fibred tissue. Few of the simple vascular canals are thinly but only incompletely lined by parallel-fibered tissue. In the Oregon material, changes in growth rate are only indicated by changes in vascular organization but no distinct growth marks were identified. The compact bone of Askeptosaurus is best comparable to some pachypleurosaurs, whereas its combination of tissue and vascularity is similar to eosauropterygians in general, except for the coarse nature of its parallel-fibred tissue. The cancellous bone of the Oregon thalattosauroid resembles what is documented in ichthyosaurs and plesiosaurs. However, in contrast to these its tissue does not consist of fibro-lamellar bone type. Tissue types of both thalattosaurian taxa indicate rather different growth rates and growth patterns, associated with different life history strategies. The microanatomy reflects different life styles that fit to the different environments in which they had been found (intraplatform basin vs. open marine). Both thalattosaurian taxa differ from each other but in sum also from all other marine reptile taxa studied so far. Thalattosaurian bone histology documents once more that bone histology provides for certain groups (i.e., Triassic Diapsida) only a poor phylogenetic signal and is more influenced by exogenous factors. Differences in lifestyle, life history traits, and growth rate and pattern enabled all these Triassic marine reptiles to live contemporaneously in the same habitat managing to avoid substantial competition.

Variant Anatomy of the Right Ventricular Moderator Band in Human Heart in Early Antenatal Period of Development

INTRODUCTION: The information about the variants of the structure and topography of the moderator band (MB) that connects the interventricular septum with the anterior papillary muscle and the anterior wall of the right ventricle in the heart of a fetus and a newborn, is of great importance for cardiac surgery.
 AIM: To establish the prevalence of the MB and describe the variants of its shape, structure and position in the right ventricle of the normal human heart in the early antenatal period of development.
 MATERIALS AND METHODS: Using Olympus SZX2-ZB10 stereomicroscope with 4.725X to 15X magnification, formalin-fixed hearts of fetuses and stillborns of 1728 weeks were studied. The results are presented in the form of median, 25th and 75th percentiles, extreme values. Correlation analysis was performed. Significance of the difference of proportions was evaluated by one-sided t-test. The results are presented in the form of median (Me), 25th and 75th percentiles (Q25%Q75%).
 RESULTS: MB was found in 73 of 90 preparations (81.1%), in 48 cases (66%) it was bridge-like, and in 24 of 72 (33.3%) ― parietal. MB had flattened (crest-like) or cylindrical shape (62.5% vs 33%; p = 0.0002). The most common was flattened bridge-like variant. The length of MB was 2.2 (1.753.0) mm, width 1.35 (0.91.75) mm, thickness 1.0 (0.651.5) mm. The band mainly originated from the interventricular septum between the middle and apical thirds of the longitudinal axis, and the anterior and middle thirds of the transverse axis of the interventricular septum. It typically terminated with the attachment to the anterior papillary muscle (47.7%), or to the anterior wall of the right ventricle immediately in front of this muscle (38.5%). In 22.2% of cases, the MB had papillary muscles on it, and in 37.5%, the secondary trabeculae extended from it to the apex of the ventricle.
 CONCLUSION: MB is a normal, but not obligatory structure of the heart in the antenatal period, its normal anatomy is variable and is manifested by typical and rare variants of the form, position, beginning and end, which in many cases can impede diagnostics and treatment of the pathology of the right ventricle.

ANATOMICAL CHARACTERISTICS OF SEPTOMARGINAL TRABECULA OF THE RIGHT VENTRICLE OF THE HUMAN FETAL HEART

Anatomical structure of right ventricular septomarginal trabecula (SMT) was studied at micro-macroscopical level in 99 preparations of human fetal heart formed without malformations and minor abnormalities, obtained at 17-28 weeks of development. SMT was found to be a constant cardiac structure consisting of the body and two branches: anterior and posterior. Body of SMT is a myocardial vallum, unseparable from the interventricular septum, the long axis of which is always located along the conventional line connecting septal insertion of supraventricular crest and right ventricular apex. Posterior margin of SMT body was distinct in 75% of cases and smoothened in 21.9%. Base of the SMT was solid in 46.3% and split into secondary trabeculae in 52.6% of cases. Narrow and wide forms of SMT body were considered as its extreme anatomical variants. It is suggested to distinguish two anatomical types of SMT: a complete type, in which SMT was represented by a complex consisting of body in the form of muscular vallum and both branches, and an incomplete one, in which one of the branches was absent. Human fetal heart SMT is characterized by a variability, which is manifested by certain combinations of anatomic variants of SMT base form, its posterior margin, and the presence, shape and mutual location of its branches.

Bone mineral properties in growing Col1a2+/G610C mice, an animal model of osteogenesis imperfecta

The Col1a2+/G610C knock-in mouse, models osteogenesis imperfecta in a large old order Amish family (OOA) with type IV OI, caused by a G-to-T transversion at nucleotide 2098, which alters the gly-610 codon in the triple-helical domain of the α2(I) chain of type I collagen. Mineral and matrix properties of the long bones and vertebrae of male Col1a2+/G610C and their wild-type controls (Col1a2+/+), were characterized to gain insight into the role of α2-chain collagen mutations in mineralization. Additionally, we examined the rescuability of the composition by sclerostin inhibition initiated by crossing Col1a2+/G610C with an LRP+/A214V high bone mass allele. At age 10-days, vertebrae and tibia showed few alterations by micro-CT or Fourier transform infrared imaging (FTIRI). At 2-months-of-age, Col1a2+/G610C tibias had 13% fewer secondary trabeculae than Col1a2+/+, these were thinner (11%) and more widely spaced (20%) than those of Col1a2+/+ mice. Vertebrae of Col1a2+/G610C mice at 2-months also had lower bone volume fraction (38%), trabecular number (13%), thickness (13%) and connectivity density (32%) compared to Col1a2+/+. The cortical bone of Col1a2+/G610C tibias at 2-months had 3% higher tissue mineral density compared to Col1a2+/+; Col1a2+/G610C vertebrae had lower cortical thickness (29%), bone area (37%) and polar moment of inertia (38%) relative to Col1a2+/+. FTIRI analysis, which provides information on bone chemical composition at ~7μm-spatial resolution, showed tibias at 10-days did not differ between genotypes. Comparing identical bone types in Col1a2+/G610C to Col1a2+/+ at 2-months-of-age, tibias showed higher mineral-to-matrix ratio in trabeculae (17%) and cortices (31%). and in vertebral cortices (28%). Collagen maturity was 42% higher at 10-days-of-age in Col1a2+/G610C vertebral trabeculae and in 2-month tibial cortices (12%), vertebral trabeculae (42%) and vertebral cortices (12%). Higher acid-phosphate substitution was noted in 10-day-old trabecular bone in vertebrae (31%) and in 2-month old trabecular bone in both tibia (31%) and vertebrae (4%). There was also a 16% lower carbonate-to-phosphate ratio in vertebral trabeculae and a correspondingly higher (22%) carbonate-to-phosphate ratio in 2month-old vertebral cortices. At age 3-months-of-age, male femurs with both a Col1a2+/G610C allele and a Lrp5 high bone mass allele (Lrp5+/A214V) showed an improvement in bone composition, presenting higher trabecular carbonate-to-phosphate ratio (18%) and lower trabecular and cortical acid-phosphate substitutions (8% and 18%, respectively). Together, these results indicate that mutant collagen α2(I) chain affects both bone quantity and composition, and the usefulness of this model for studies of potential OI therapies such as anti-sclerostin treatments.

Morphology analysis of vertebral trabecular bone under dynamic loading based on multi-scale theory

Trabecular bone has a complicated porous microstructure and consists of interconnected plates and rods known as trabeculae. The microarchitecture of the trabeculae contributes to load distribution capacity and, particularly, the optimal bone strength. Many previous studies have shown that morphological parameters are used to characterize the microarchitecture of trabecular bone, but little is known about the mechanical role of trabecular morphology in the context of load-bearing behavior. Therefore, this study proposes a new segmentation method for examining the morphology of trabecular structure foci of load-bearing capability. A micro-finite element model of trabecular bone was obtained from the fourth lumbar vertebra on the basis of a three-dimensionally reconstructed micro-computed tomography (CT) image. We used an asymptotic homogenization method to determine microscopic stress by applying three unidirectional compressive loads in the vertical, anteroposterior, and right-left axes of two trabecular bone volumes. We then classified the complicated trabecular microstructure into three segments: primary and secondary trabeculae and trabeculae of no contribution. Next, a dynamic analysis was conducted by applying a force impulse load. The result indicated that 1/3 of the trabecular volume functions as primary trabecula. The morphology of the trabecular network could be visualized successfully highlighting the percolation of the stress wave in the primary trabecular segment. Further, we found that the role of the plate-like structures was that of a hub in the trabecular network system.

Identification of trabecular excrescences, novel microanatomical structures, present in bone in osteoarthropathies

It is widely held that bone architecture is finely regulated in accordance with homeostatic requirements. Aberrant remodelling (hyperdensification and/or cyst formation in the immediately subchondral region) has previously been described in bone underlying cartilage in arthropathies. The present study examined the trabecular architecture of samples of bone, initially in the severe osteoarthropathy of alkaptonuria, but subsequently in osteoarthritis using a combination of light microscopy, 3D scanning electron microscopy and quantitative backscattered electron scanning electron microscopy. We report an extraordinary and previously unrecognised bone phenotype in both disorders, including novel microanatomical structures. The underlying subchondral trabecular bone contained idiosyncratic architecture. Trabecular surfaces had numerous outgrowths that we have termed "trabecular excrescences", of which three distinct types were recognised. The first type arose from incomplete resorption of branching secondary trabeculae arising from the deposition of immature (woven) bone in prior marrow space. These were characterised by very deeply scalloped surfaces and rugged edges. The second type had arisen in a similar way but been smoothed over by new bone deposition. The third type, which resembled coarse stucco, probably arises from resting surfaces that had been focally reactivated. These were poorly integrated with the prior trabecular wall. We propose that these distinctive microanatomical structures are indicative of abnormal osteoclast/osteoblast modelling in osteoarthropathies, possibly secondary to altered mechanical loading or other aberrant signalling. Identification of the mechanisms underlying the formation of trabecular excrescences will contribute to a better understanding of the role of aberrant bone remodelling in arthropathies and development of new therapeutic strategies.

Morphogenetic aspects of the septomarginal trabecula in the human heart

IntroductionThe septomarginal trabecula is a constant element of the anatomy of the human heart, which connects the interventricular septum and the anterior wall of the right ventricle. Considering the diversity of opinions about the structure and numerous studies suggesting its important role in haemodynamics and conduction of electrical impulses in the heart, we decided to study this element in detail.Material and methodsThe research was conducted on 220 human hearts. Attention was mainly paid to the structure and topography of the trabecula. Its relation to the anterior papillary muscle was also a part of the study.ResultsThe presence of this morphologically diverse element was confirmed in each of the studied hearts. In most cases the trabecula originated from the upper part of the interventricular septum, separating at an angle increasing proportionally to the number of branches of the crista supraventricularis as well as the number of secondary trabeculae. The criteria established for the study, which included the course of the trabecula in the lumen of the right ventricle and its relation to the anterior papillary muscle, let us distinguish 4 types of septomarginal trabecula (I, II, III, IV). The most common was type III, the undivided trabecula, tightly connecting with the anterior papillary muscle.ConclusionsBased on the results of the following study we propose a hypothesis on the genesis of respective parts of the septomarginal trabecula and a plausible sequence of changes they undergo during human ontogenesis and phylogenesis of the primates.

Osteopontin Distribution in the Canine Skeleton during Growth and Structural Maturation

The distribution of osteopontin (OPN) was studied immunohistochemically in cells and extracellular matrix in the humerus, scapula, and lumbar vertebrae of growing (age: 6 weeks, 12 weeks, 4.5 months) and adult dogs. OPN was expressed in hypertrophic chondrocytes of epiphyseal cartilage and in chondrocytes of the deep zone of mature articular cartilage, where extracellular matrix was also stained. OPN expression was strongest in 4.5-month-old puppies in cells of the osteoblastic lineage. It also varied with microlocation and was pronounced in areas prone to resorption due to modelling and remodelling activities. Osteoclasts were always strongly labelled with OPN. OPN deposition in extracellular bone matrix was detected particularly as a delineation of cartilage cores within secondary trabeculae and as a lining of the trabecular surfaces in resorption microlocations. The OPN distribution pattern is discussed here for each cell population with regard to its functional implications.

Unresolved issues in osteoporosis in men.

Fragility fractures in men are a public health problem. The increasing longevity in men is likely to increase the public health burden of fractures in men. This problem remains unrecognized by doctors, the public and governments. About one third of all hip fractures occur in men but the incidence and gender ratio varies from country to country for reasons that are not understood. The prevalence of spine fractures is about half that of women in most studies, but similar to that of women in several other studies. The incidence of spine fractures is uncertain but is likely to be about half that of women except in 80+ year olds, when it appears to be similar. The causes of the higher mortality in men than in women following hip or spine fracture are not well defined. Areal bone mineral density (aBMD) predicts fracture risk in men; the relative risk for spine and hip fracture conferred by a 1 SD lower aBMD, or by a prevalent fracture, is similar in men and women. The age-specific absolute risk (number of cases per 1,000 per year) conferred by a given hip aBMD is similar in men and women. The age-specific absolute risk conferred by aBMD at the calcaneus or radius for spine fracture is similar for men and women. If the absolute and relative risks are similar then the lower incidence of fractures in men than women may reflect the lower proportion of the male population distribution below a given structural determinant of bone fragility. That is, at any age, there may be fewer men than women with smaller bones, lower volumetric bone mineral density (vBMD), thinner trabeculae or cortices, architectural disruption, or higher remodeling rates. Higher mortality and fewer falls may also contribute to the lower incidence of fractures in men. This tail end of the male population distribution (for traits like bone size, vBMD, architecture, and remodeling rates) is the likely source of fracture cases in males. Hypogonadism is a risk factor for osteoporosis. However, the definition, prevalence, causes and structural consequence of hypogonadism are inadequately defined. At what level of testosterone is bone balance negative? What structural determinants of axial and appendicular strength are regulated by testosterone, estrogen, growth hormone (GH), insulin like growth factor 1 (IGF-1) (or their interactions)? Is reduced bone size in men with spine or hip fractures due to failed growth-related or age-related periosteal expansion? If reduced vBMD is due to reduced accrual, is this due to reduced cortical thickness? What factors regulate and coregulate the periosteal and endocortical modeling and remodeling? Are reduced trabecular numbers due to failed formation at the growth plate, excess resorption of primary trabeculae or reduced formation of secondary trabeculae? Is reduced trabecular thickness due to failed prepubertal or pubertal bone formation? Is reduced cortical and trabecular thickness during aging due to excessive endosteal resorption or reduced bone formation? If the former, is this due to increased remodeling sites or increased resorption depth? Most evidence favors reduced bone formation as the cause of bone loss with trabecular bone loss occurring by reduced formation and thinning more than by increased resorption and loss of connectivity. Cortical bone loss is less than in women because endocortical resorption is less and periosteal apposition is greater. If the reduced bone formation is most important, is this due to reduced osteoprogenitors, reduced osteoblast matrix synthesis or early osteoblast apoptosis? Anti-spine-fracture efficacy has been demonstrated in only one randomized heated with alendronate drug in men. The gaps in our knowledge remain large.

Static and dynamic bone histomorphometry in children with osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a genetic disorder characterized by increased bone fragility and low bone mass. Four clinical types are commonly distinguished. Schematically, type I is the mildest phenotype, type II is usually lethal, type III is the most severe form compatible with postnatal survival, and type IV is moderately severe. Although mutations affecting collagen type I are responsible for the disease in most patients, the mechanisms by which the genetic defects cause abnormal bone development have not been well characterized. Therefore, we evaluated quantitative static and dynamic histomorphometric parameters in tetracycline-labeled iliac bone biopsies from 70 children, aged 1.5 to 13.5 years, with OI types I (n = 32), III (n = 11), and IV (n = 27). Results were compared with those of 27 age-matched controls without metabolic bone disease. Biopsy core width, cortical width, and cancellous bone volume were clearly decreased in all OI types. Decreased cancellous bone volume was due to a 41%–57% reduction in trabecular number and a 15%–27% lower trabecular thickness. Regression analyses revealed that trabecular number did not vary with age in either controls or OI patients, indicating that no trabecular loss occurred. The annual increase in trabecular thickness was 5.8 μm in controls and 3.6 μm in type I OI, whereas no trabecular thickening was evident in type III and IV OI. Wall thickness, which reflects the amount of bone formed during a remodeling cycle, was decreased by 14% in a subgroup of 17 type I OI patients, but was not determined in the other OI types. The remodeling balance was less positive in type I OI than in controls, and probably close to zero in types III and IV. Surface-based parameters of bone remodeling were increased in all OI types, indicating increased recruitment of remodeling units. No defect in matrix mineralization was found. In conclusion, there was evidence of defects in all three mechanisms, which normally lead to an increase in bone mass during childhood; that is, modeling of external bone size and shape, production of secondary trabeculae by endochondral ossification, and thickening of secondary trabeculae by remodeling. Thus, OI might be regarded as a disease in which a single genetic defect in the osteoblast interferes with multiple mechanisms that normally ensure adaptation of the skeleton to the increasing mechanical needs during growth.

The spleen of the one humped camel (Camelus dromedarius) has a unique histological structure

The histology and structure of 38 spleens of the dromedary (aged 0.5-15 y) were studied in relation to age. The spleen was found to have a thick capsule (292+/-106 mm) divided into an outer layer (113+/-39 mm) composed mainly of connective tissue and an inner layer (180+/-81 mm) consisting mainly of smooth muscle cells. Vascular and avascular trabeculae extend from the capsule, the former containing arteries and nerves but no trabecular veins, the latter being divided structurally into primary and secondary trabeculae. Subcapsular and peritrabecular blood sinuses around primary and vascular trabeculae are unique to the camel spleen. The central artery emerges from the periarterial lymphatic sheath and branches into up to 4 penicilli which extend as sheathed arterioles (42+/-8 microm). These are found near or surrounded by blood sinusoids of the red pulp. A wide marginal zone surrounds the white pulp and contains sheathed arteries but no marginal sinuses. The red pulp is characteristically divided into cords by secondary trabeculae and contains venous sinusoids of different sizes. The camel spleen is of a sinusal type that can store blood. The thick muscular capsule and trabeculae pump the stored blood according to the body's need. Both closed and open circulations are found. The venous return is unique as the blood flow is from the venous sinusoids of the red pulp to the peritrabecular sinuses to the subcapsular sinuses to the splenic vein. No significant structural differences related to age were found.

Effects of vitamin K2 and calcitonin on bone resorption model induced by vitamin A in thyroparathyroidectomized rats

Vitamin K2 is considered to have two different effects: one is to enhance bone formation, and the other is to suppress bone resorption. However, as these effects have not been observed in a single experiment, it is unclear whether bone formation can proceed during a state of accelerating bone resorption. We therefore examined the effects of vitamin K2 and calcitonin on a vitamin A-induced bone resorption model of thyroparathyroidectomized rats using bone histomorphometry and bone metabolism markers. The seven groups of male Sprague-Dawley rats (6 weeks old) were sham operation of thyroparathyroidectomy (TPTX) (sham group), TPTX (TPTX group), treated with vitamin A (20 mg/kg per day) from 11th to 20th day after TPTX (A group), treated with vitamin A and vitamin K2 (30 mg/kg per day) or its vehicle from 11th to 20th day after TPTX [K group or K (veh) group], and treated with vitamin A and calcitonin (10IU/kg/ per day) or its vehicle during the same period [CT group or CT (veh) group]. Serum and urine samples were taken for marker determination on days 10, 13, 16, and 19 of TPTX and at death on the 21st day after TPTX. Undecalcified sections (Villanueva bone stain) were made of the left tibiae and decalcified sections [tartrate-resistant acid phosphatase (TRAP) stain] of the right tibiae. In the undecalcified sections, secondary trabeculae were used for histomorphometry, and in the decalcified sections primary and secondary trabeculae were used. Serum Ca of the vitamin A-administered group was significantly higher than that of the TPTX group, but this change was inhibited by vitamin K2 or calcitonin. Serum alkaline phosphatase (ALP) in the K group was significantly higher than in all the thyroparathyroidectomized groups except the K (veh) group. In the undecalcified sections, although there was no significant difference between any of the groups in bone volume, the K group showed an increase of osteoid surface and mineralizing surface. In the decalcified sections, the K group showed a decrease of TRAP-positive areas compared to the K (veh) group in primary trabeculae. There was no significant difference between the K and K (veh) groups in secondary trabeculae. Results from the CT group were compatible with bone resorption inhibition in both bone metabolism markers and bone histomorphometry. We found that vitamin K2 enhances bone formation and suppresses bone resorption in areas with a high turnover of bone metabolism. Vitamin K2 is therefore expected to increase bone content if it is administered over an extended period.

Intramembranous trabecular generation in normal bone

The ability of trabeculae to reform following localized ablation may provide further insight into the sequence of events in cancellous regeneration. Histological features of cancellous repair were examined in the iliac crest of aged female sheep at intervals after removal of a 1-cm diameter biopsy. Comparison was made with normal intramembranous trabecular formation in the foetal lamb. The first immature trabeculae to form in the defects within 3 weeks were exclusively intramembranous, not endochondral, and the systematic process was indistinguishable from that in the intact growing foetal lamb. In both the young and old skeleton, two features were prominent. First, the damaged endosteum of the sheep functioned like the intact periosteum of the lamb to produce orderly migrating arrays of discrete coarse collagenous fibres, 5–25 µm thick, which penetrated the surrounding soft tissues to form a polarised preliminary framework. Without this structure, primary trabecular development did not take place. Throughout subsequent bone apposition the preliminary framework, which bonded hard to soft tissues and new bone to old, remained largely unmineralised. Second, intratra-becular resorption channels divided the established, thickened primary bars into networks of mature secondary trabeculae. It is concluded that the two features are central and universal to trabecular proliferation and may provide a morphological basis for future trabecular restitution of the depleted elderly skeleton.

The Histopathology of Camptomelia (Bent Limbs)

Camptomelia is well established syndrome in which the most prominent osseous feature is bowing of the long bones. Although several patients have died, usually due to respiratory insufficiency caused by defects of the cartilage of the tracheal rings and lower respiratory tract, histologic studies of the bone in camptomelia have led to conflicting conclusions about pathogenesis. A complete autopsy of a neonatal case, including serial sections of the long bones, revealed normal enchondral growth sequences of the epiphyseal plate. In the diaphysis, centering around the angle of the bend, the cylinderization process was markedly abnormal. Extensive new secondary trabeculae formed on the concave (posterior) surface of the bone during resorption on the convex (anterior) surface. A cone of dense new bone formed at the apex at the convex anterior angle of the bend. These findings supported previous suggestions that bone formation and remodeling processes were normal. With the variation of bone involvement in different patients, these features indicate that camptomelia is the result of an abnormality of cartilage anlage formation, probably owing to a transient exogenous teratogen. Camptomelia is the preferred term. Basically, the syndrome is a dyschondrogenesis.

Morphological effects of torsion applied to growing bone. An in vivo study in rabbits.

In order to study the effect of pure torsional forces upon the rotational development of the growing tibia, 35 immature rabbits underwent torsional loading of one tibia in vivo with a spring-loaded cylinder while the other tibia was a control. The radiographic results showed rotation occurring only at the epiphysial plate. Histologically this was assocaited with angulation of the hypertrophic cartilage columns occurring as little as 24 hours after loading which with longer periods of loading produced angled primary and secondary trabeculae. Radiographic and histological analyses of the diaphysis using tetracycline labelling and Spalteholtz injection techniques failed to show any evidence of cortical remodelling or reorientation of the cortical vessels of a rotational nature, suggesting that rotational modelling occurs solely at the epiphysial plate.

Microanatomy of the lung parenchyma of a tegu lizard Tupinambis nigropunctatus.

The combined techniques of light microscopy, scanning (SEM) and transmission (TEM) electron microscopy were used for the first time to study the structure of unicameral lungs of a Tegu lizard (Tupinambis nigropunctatus). The lungs are prolate spheroid bags with blood supplied by superficial branches of a dorsal pulmonary artery and returned by diffuse, more deeply located veins. The primary bronchus enters the medial aspect near the apex of the lung. The lung wall is composed of trabeculae: (1) arranged in a faviform pattern, (2) forming individual faveoli (gas exchange chambers) which appear deepest in the cranial one-half of the lung, (3) all of which have a smooth muscle core overlain by either a ciliated or nonciliated epithelium. A ciliated epithelium lines the luminal surfaces of the large primary trabeculae and parts of smaller secondary trabeculae; it is composed of cone-shaped cells with ciliated-microvillous surfaces, and of columnar serous secreting cells. Nonciliated epithelium covers the luminal surface of portions of some secondary trabeculae, abluminal surfaces of primary and secondary trabeculae and all surfaces of the small tertiary trabeculae forming the faveoli. The nonciliated epithelium overlies an extensive superficial capillary network. The blood-gas barrier (0.7-1.0 μm thick) is composed of a thin cytoplasmic flange of Type I pneumonocytes, a thick homogeneous basal lamina and an attenuated endothelial cytoplasm. Numerous surfactant-producing Type II pneumonocytes are closely associated with the Type I pneumonocytes. The nonrespiratory ciliated epithelium may function in humidification of air and clearing of the lungs.

The effect of orally administered zinc sulfate on extraction wound healing in hamsters

Orally administered zinc sulfate was found to cause a statistically significant acceleration in the rate of healing of extraction wounds in hamsters. The greatest acceleration was observed during the first postoperative week. After one week, the differences between the control and experimental groups were less dramatic. Bone formation, however, was still accelerated in the experimental group throughout the time of the study. Not only was there an acceleration in the rate of bone formation, but the process of maturation of osteoid tissue to mature secondary trabeculae was also accelerated.