Subcapital fracture of the hip following an intertrochanteric fracture. A case report and literature review

A 42-year-old alcoholic man who had a normal femoral head histologically incurred a subcapital fracture four months after surgical treatment of an intertrochanteric fracture of the same hip. Subcapital fracture of the hip following intertrochanteric fracture is an unusual occurrence, with possibly as few as 11 cases documented in the literature. Affected persons are usually elderly females with severe osteoporosis. Though unusual, the fracture is obvious and not difficult to treat.

Charged beads: generation of bone and giant cells

Based on reports of electrically induced bone formation and findings that some materials used to promote bone ingrowth are stimulatory in bead form, the osteogenic potential of beads with different surface charges was examined. In this preliminary study, three types of Sephadex beads were injected into chick femora: type I, DEAE beads, positively charged; type II, CM beads, negatively charged; type III, G-25, uncharged. Beads were injected into the femoral midshaft, and after 3 days, 4 days, and 1 week, birds were sacrificed and femora were processed for histology. Type I beads: at 3 days, were surrounded by multinucleated giant cells; by 4 days, patches of bead-associated new bone were present along with giant cells; after 1 week, occasional bead-associated multinucleated cells were seen, but now most beads were surrounded by new intramedullary bone, forming an extensive bead-bone lattice. With bead types II and III, bead-associated new bone was seen at 3 days and 4 days only when beads lodged near the endosteum or in the metaphysis. At 7 days, no bone was seen with either of these two bead types. The response to the type I beads may be likened to a remodeling phenomenon with large numbers of giant cells at 3 days, new bone and giant cells at 4 days, and evidence only of bone formation at 7 days.

The effect of low dietary calcium and calcium supplementation on calcium metabolism and bone in the immature, growing rat

The data presented here were obtained from a series of experiments designed to determine 1) whether normal growth and bone development could be maintained in young, growing rats (3-9 weeks of age) on a diet containing 0.1% Ca, and 2) whether Ca presented in a bolus would be utilized as effectively as the same amount of Ca distributed throughout the diet. Weanling female rats were raised to 9 weeks of age on diets containing 0.4% P and either 0.5% or 0.1% Ca. One group of animals on the 0.1% Ca diet was given oral supplements of CaCO3 twice each day to supply the same amount of Ca consumed by age-matched animals on the 0.5% Ca diet. We found that animals consuming diet containing 0.1% Ca grew at the same rate as animals receiving 0.5% Ca, or 0.1% Ca + supplement for up to 9 weeks of age when the experiment was terminated. Measurement of femur length indicated that long bone length was the same for all animals. However, the 0.1% Ca group exhibited mild hypocalcemia (9.1 mg/dl vs 10.4 for controls), a 2.6-fold elevation in immunoreactive parathyroid hormone, and an increase of similar magnitude in circulating levels of 1,25-dihydroxyvitamin D. Bones from the 0.1% Ca group contained less than half as much Ca as bones from the 0.5% Ca group, and exhibited significant decreases in mid-shaft diaphyseal thickness, % trabecular volume of the distal metaphysis and breaking strength (torsion testing). These results suggest that while a diet containing 0.1% Ca is able to maintain normal growth, bone mineralization is compromised.(ABSTRACT TRUNCATED AT 250 WORDS)

Regional alterations in long bone produced by internal fixation devices. Part I. 85Sr clearance

We examined the effect of rigid plate application on the radiostrontium clearance of the intact canine femur at 6 months. We examined each of the component surgical steps. We calculated the clearance both for the whole bone and for each of the five transverse sections of the whole bone. Screw application, but not drilling, increased the clearance in the segment about the screw holes. Plate application produced an increase in the segment beneath the plate as well as around the screws and in the whole bone. These changes are accomplished not only by an absolute increase in clearance to the middle three segments, but by a relative diminution in clearance by the most proximal and distal segments. The histomorphometric changes in long bones following rigid plating may be accompanied by regional increases in bone blood flow.

Regional alterations in long bone 85Sr clearance produced by internal fixation devices. Part II. Histomorphometry

The effects of each of the surgical stages involved in compression plating on the development of cortical thinning and porosity were assessed in the intact midshaft, stress-shielded femoral segments of adult mongrel dogs 6 months postoperatively. The data were evaluated in terms of a postsurgical tetracycline-based measure of remodeling and terminal 85Sr clearance (SrC) values for the plated segments of bone. Drilling had no effect on any parameter. Screw application was associated with minimal cortical thinning (p less than 0.05), while plate fixation clearly promoted thinning (p less than 0.01) and porosity (p less than 0.05). The percentage of labeled osteons, a measure of remodeling activity, increased only after plate fixation (p less than 0.05), and the labeling patterns suggested that most osteons had formed during the first 4 postsurgical months. That none of these changes were correlated with the 6-month SrC values suggests that the development of plate-induced osteopenia involves disparate histomorphometric time constants, rather than lack of any association.

Pull-out strengths of bone screws at various sites about the pelvis--a preliminary study

The pull-out strength of both cortical and cancellous screws from bone at various sites about cadaveric pelves was examined. No significant differences were seen between cortical or cancellous screws at similar sites with the possible exception of the sacroiliac joint. Pull-out strengths were best correlated to the depth of bone at a particular screw hole. For practical purposes, the strongest sites are in the thick buttress of bone along the iliopubic column.

Radiostrontium clearance and bone formation in response to simulated internal screw fixation

Changes in radiostrontium clearance (SrC) and bone formation (tetracycline labeling) were observed in the femurs of skeletally mature dogs following the various operative steps involved in bone screw fixation. Drilling, but not periosteal stripping, produced a small but statistically significant increase in SrC and endosteal bone formation in the distal third of the bone. Strontium clearance values equivalent to those produced by drilling alone were recorded after screw fixation at low or high torque (5 versus 20 inch pounds), as well as by the insertion of loosely fitting stainless steel implants. Bone formation (equals the percentage tetracycline-labeled trabecular bone surfaces) was increased by 30% when SrC values exceeded 3.5 ml/100 g bone/min, and the relationship was linear when SrC values ranged between 1.0 and 7.0 ml/100 g bone/min. The changes in SrC and bone formation one-week after bone screw application are primarily those associated with a response to local trauma caused by drilling.

Bone maturation and quality of bone material in rats flown on the space shuttle 'Spacelab-3 Mission'

The maturation profiles of calcium, phosphorus, magnesium and hydroxyproline in the femoral trabecular and cortical bone and in the thoracic vertebrae from male rats flown on the 7-day 'Spacelab-3 Mission' were measured by density gradient analysis. In rats exposed to a spaceflight environment, profiles of the matrix and mineral moieties were shifted toward both the lower (vertebrae) and higher density fractions (femurs and vertebrae), patterns indicating a decrease in bone growth/turnover. X-Ray diffraction of vertebrae indicated that spaceflight is associated with a decrease in apatite crystal size/perfection.

Bone deficit in ovariectomized rats. Functional contribution of the marrow stromal cell population and the effect of oral dihydrotachysterol treatment

This study investigates the proliferative and osteogenic role of marrow stromal/osteoprogenitor cells in the development of the cortical bone deficit in ovariectomized (OVX) female rats. In vitro, clonal growth of marrow stromal cells from OVX rats was significantly impaired (vs. sham-operated controls). Yet in vivo, cells from sham-operated and OVX rats had equal osteogenic potential in several in vivo experimental situations, such as in intraperitoneally implanted millipore diffusion chambers and in intramuscular implants of marrow plus osteoinductive bone matrix (composite grafts). Long-term (6 mo) dihydrotachysterol (DHT) treatment of OVX rats enhanced their in vitro proliferative potential and clonal growth, as well as their osteogenic expression in composite grafts. The observation that the in vivo osteogenic performance of OVX rat marrow stromal cells was normal at extraosseous sites suggests that the mechanisms leading to osteopenia may involve an abnormality in cell-matrix interactions.

The changes in quality of mandibular bone mineral in otherwise totally immobilized rhesus monkeys

The status of bone mineral and osteocalcin in the young adult Rhesus monkey mandible was assessed following a 14-day period of postcranial immobilization, and after 7- and 28-day recovery periods. Specimens of cortical bone taken from the compact bone at the inferior border of the jaws were ground in liquid nitrogen and sieved to a particular size below 20 micron. The bone powder was then fractionated in a bromoform-toluene density gradient to determine its mineralization profile (Ca, P, CO3, and osteocalcin), and X-ray diffraction was used to determine apatite crystal size in some fractions. There was no change in the chemistry of the mandibular bone from the immobilized animals. However, the mineralization profile in that group showed a significant shift toward the higher density fractions, indicating the presence of a greater than normal content of mature well-mineralized bone. While this trend was accentuated in the jaws following a 7-day postimmobilization recovery period, partial recovery of the normal profile was observed after a 28-day recovery period. The osteocalcin profile shifted like the mineralization profile during the immobilization and recovery periods. X-ray diffraction analyses showed that the shift in the mineralization profile during the immobilization period was associated with a decrease in apatite crystal size.

Effect of rotopositioning on the growth and maturation of mandibular bone in immobilized rhesus monkeys

As part of an ongoing effort to mimic the hypokinesia and hypogravity of spaceflight, the effects of 14 d immobilization and rotopositioning on mandibular bone osteon growth (= radial rate of closure) was assessed in 12 juvenile Rhesus monkeys by tetracycline labeling. The monkeys had been restrained in a supine position and rotated 908 every 30 min through a full 3608 arc for 14 d. Osteon growth was also assessed after the immobilized/rotopositioned animals had been permitted to recover in metabolism cages for periods of 28 and 56 d. The closure rates of osteons in the cortex of the inferior border of the mandible were not abnormal during immobilization/rotopositioning or during recovery. The regression line plots yielded slopes of: Controls = 0.946-1.000; Immobilized/Rotopositioned = 1.045; 28 d Recovery = 0.833; 56 d Recovery = 0.829. Microradiographs indicated a normal distribution of osteons of different mineral density: lowly (28%), moderately (53%), and highly mineralized (18%). Bone porosity values also remain within the normal range (18.3 6 4.1%). These results suggested that 14 d immobilization/rotopositioning did not effect abnormal changes in the rates of bone formation and mineralization in the mandibular cortex of the juvenile Rhesus monkey.

Fracture healing perspectives

This paper reviews the sequence of histomorphologic changes that occur in and around a fracture site, and discusses recent concepts about the roles of the cells and bone matrical moieties in promoting specific cell transformations during the phases of callus tissue formation and consolidation of the bony cortex. Current knowledge about the roles of autocrine, paracrine, and endocrine polypeptide growth and transforming factors lends new perspectives about this classic problem in bone physiology.

In vitro evaluation of circadian patterns of bone collagen formation

The circadian patterns of bone collagen formation were studied in vitro to ascertain whether the biorhythmic profiles previously measured in vivo reflect true differences in collagen synthesis. Alteration of amino acid pool sizes did not negate the circadian-stage differences in bone collagen production. Evaluations of proline uptake and transport, as well as collagenous protein turnover, demonstrated that the intracellular assembly and secretion of bone collagenous protein during the dark span is truly decreased relative to that during the light period. It was further affirmed that PTH is essential for maintenance of the normal circadian collagen synthesis rhythms.

Effect of an adrenocorticotropin analogue, ACTH 1-17, on DNA synthesis in murine metaphyseal bone

The effects of injections of a synthetic adrenocorticotropin (ACTH 1-17, Synchrodyn) on the rate of DNA labeling in the metaphyseal bone of CD2F1 mice were tested on a chronopharmacological dosing schedule. Groups of mice that had been conditioned to a 12-hr light/12-hr dark schedule were injected at one of six different timepoints, 4 hr apart, during a single 24-hr span with either a low (0.02 I.U./kg) or a high (20 I.U./kg) dose of ACTH 1-17. Control groups received injections of a placebo at corresponding timepoints. Subgroups of mice were injected with [3H]thymidine ([3H]Tdr) to follow the changes in DNA labeling in the proximal tibial metaphysis at 15 min and 2, 4, 8, 12 and 24 hr after ACTH 1-17 or placebo treatment. All mice were injected with the isotope 30 min before killing, except for those killed 15 min after Rx administration where the isotope had been injected 14 min before killing. The data were analyzed both by analysis of variance and by the cosinor method, the latter of which tests the fit of a 24-hr cosine curve to the data. The effect of ACTH 1-17 on the target cell population was dependent not only upon the dose but upon the time of administration. Both doses exerted time-dependent action, ranging from stimulation to inhibition of DNA labeling. Inhibition was noted when the ACTH 1-17 was administered at 2 hr after the beginning of the daily dark span when nocturnal animals become active. When administered at this circadian stage, the larger dose in particular was associated with an inhibition of DNA labeling lasting for 24 hr. The inhibitory effect was much shorter when the same dose was injected 4 hr earlier. Moreover, the large ACTH 1-17 dose had a stimulatory effect lasting for 24 hr when it was administered 2 hr after the onset of the daily light span, with a much shorter stimulation following administration of the large dose at 6 hr after the beginning of the daily dark span. A circadian stage-dependent stimulation or inhibition of DNA labeling at 2 or 14 hr after light onset, respectively, was thus complemented by an initial inhibition followed by stimulation and vice versa at 10 and 18 hr after light onset respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of fixation devices on radiostrontium clearance in the intact canine femur

Femoral metaphyseal/diaphyseal blood flow was studied by 85Sr clearance in unfractured segments of dog femurs following compression plating and various control procedures (drilling with and without application of screws). The animals were tested as early as seven days and as late as two months after surgery. The only statistically significant change in strontium clearance (SrC) was an increase produced by the application of stainless-steel bone screws, with or without plates. The presence or absence of compression had no consistent effect on changes in the rate of SrC. During the period of study, no changes in bone mineralization, haversian porosity, or cortical bone thickness accompanied the SrC alterations.

3-D femoral stress analysis using CT scans and p-version FEM

The potential of the finite element method as a computational aid for making objective clinical decisions has not yet been exploited due to the unreliability of the results obtained. The main reasons for this may be attributed to the poor quality of the finite elements available in the conventional softwares, improper modeling of the three dimensional problem, and errors introduced by incorrect representation of geometry and material properties. Herein, we report an attempt to derive a three-dimensional finite element model for the adult human femur which permits reliable representation of the local stress patterns. The geometry was obtained by serial computed tomography scans. The mechanical properties were based on laboratory tests and information available in the literature. The analysis is performed with a new generation software. Preliminary results suggest that the scheme could be automated and used for in vivo analysis.

Adrenal/parathyroid regulation of DNA, collagen and protein synthesis in rat epiphysial cartilage and bone

Young, growing rats which had been chronically (2 weeks) adrenalectomized or parathyroidectomized were used to define the roles of the adrenal and parathyroid glands on the maintenance of normal circadian rhythms of DNA, collagen and non-collagen protein synthesis in the skeleton. The animals were conditioned to food being available ad libitum and to 12 h light: 12 h darkness (lights on from 08.00 to 20.00 h). The pace of DNA, collagen and non-collagen protein synthesis in different regions of the tibia (tibial growth cartilage, metaphysial bone and diaphysial bone) was measured by the in-vivo incorporation of tritiated thymidine (1 h) and radioactive proline (48 h). In intact rats there were no regional differences in the phasing of the circadian profiles; peak DNA and non-collagen protein synthesis occurred at the onset of the dark period while peak collagen synthesis occurred during the middle of the period of light. Adrenalectomy selectively abolished the regional DNA synthesis rhythms without altering the phases of the serum Ca and phosphorus (P) rhythms, which peak at mid-day and at the onset of darkness respectively. Parathyroidectomy abolished the regional rhythms for collagen and non-collagen protein synthesis and serum Ca rhythms, without altering the phase of the serum P and corticosterone rhythms. Dietary Ca-lactate supplements, which raised serum Ca levels towards normal in parathyroidectomized rats, were able to correct serum corticosterone values but did not normalize bone collagen and non-collagen protein synthesis values. These data indicate that the adrenal rhythm governs the proliferative activities of bone and cartilage cells, and that parathyroid hormone is essential to maintain normal collagen and non-collagen protein synthesis rhythms.

Mineralization in rat metaphyseal bone exhibits a circadian stage dependency

Density gradient fractionation analysis of rat metaphyseal bone was used to delineate the biorhythmic changes in bone matrix mineralization. Seventy-two 4-week-old rats were entrained to 12-hr light, 12-hr dark cycles (light, 0800-2000 hr; darkness, 2000-0800 hr) for 4 weeks. All animals were fed ad lib. on Purina laboratory rat chow and tap water. Groups of 10-12 rats were killed by cervical dislocation at 4-hr intervals during a 24-hr period, and the tibias were then biopsied and frozen in liquid N2. Metaphyseal bone was fractionated via bromoformtoluene density gradients into specific gravity fractions ranging from 1.7 to 2.8. Density gradient fractions were analyzed for concentrations of calcium and inorganic phosphorus. Chronograms indicated that the accumulation of both calcium and inorganic phosphorus into the newly forming/least-dense mineral moieties of bone (1.3-1.7 sp grav) showed a single peak in the biorhythm of the rat. A statistically significant circadian rhythm of mineralization was detected for calcium (P less than 0.001) and inorganic phosphorus (P less than 0.039), with peaks during the environmental dark span. These results suggest that the physiological phasing of bone mineralization in the light-dark synchronized rat, is similar to that previously noted for cartilage mineralization and is antiphasal to the midday peak in bone collagen synthesis.

Intestinal microflora as potential modifiers of sensitizer activity in vivo

Treatment of mice (some bearing Lewis Lung tumors), with penicillin (PEN) at 500 mg/l drinking water for one week prior to treatment with misonidazole (MIS), resulted in: the elimination of their anaerobic cecal flora; a decrease in MIS-induced neurotoxicity; an increase in pharmacological exposure to MIS; a decrease in MIS chemopotentiation; a probable increase in MIS radiosensitization; an increase in MIS induced hypothermia. Assuming no chemical interaction between PEN and MIS, these observations indicate that the intestinal microflora can influence the activity of MIS in vivo. Therefore their influence should be considered in all sensitizer-related studies in vivo. The observed reduction in the neurotoxic but not the radiosensitizing potential of MIS following PEN treatment indicates a therapeutic benefit.

From bone lining cell to osteocyte--an SEM study

We describe the SEM appearance of the rat endosteal bone lining cell ( BLC ) population, and the sequence of morphological changes of these cells as they self-incorporate into unmineralized bone matrix (osteoid), establish intercellular connections, and construct lacunae. The osteoblast/nascent osteocyte series was progressively unsheathed by gentle digestion of the osteoid with 0.25% collagenase. The osteoblasts which leave the polygonally packed BLC compartment rapidly develop numerous complexly branched processes that contact the processes elaborated by previous generations of maturing and mature osteocytes. As osteoblasts mature and approach the mineralization front, they appear to lose processes. The mature cells begin to form osteocyte lacunae by depositing an asymmetric perimeter of woven collagen fibrils, such that as the cells roof-over, the lacunae appear as pocketlike constructions. The collagen fibrils on the perilacunar matrix are oriented in a tangential or circular pattern, while those in the more distal matrix are arranged in a parallel pattern. With the completion of a lacuna, its wall appears to mineralize quickly, for lacunae could be recognized only when they are forming.

The effects of spaceflight on the mineralization of rat incisor dentin

The lower incisors of Male Wistar rats flown for 18.5 days on the Soviet Cosmos-1129 Biosatellite were sectioned and chemically analyzed with an electron microprobe in order to determine whether there were specific effects of spaceflight on dentin formation/mineralization. Control tissues were obtained from rats housed under identical conditions in a land-based mock-up of the Biosatellite. The profiles of calcium (Ca), phosphorus (P), and sulfur (S) concentrations in dentin were measured in continuous traverses (1.0 micron intervals) from the pulp to the dentinoenamel junction. The incisor dentin formed during spaceflight had higher than normal (at 1G) concentrations of Ca (+ 10-15%) and P (+ 20-30%), particularly in the temporally youngest tissues within 80 micron of the pulp which had been least affected by secondary mineralization. The S-concentration profiles tended to decrease with tissue age. Fourier analysis (to determine the growth rhythms) revealed abnormal distributional patterns of S in the recently formed dentin from the Flight rats. The sulfur fluctuations in Flight animals alone periodically peaked above the irregular background fluctuations. These observations indicate that spaceflight has measureable effects on dentinogenesis, and they may also bear on the problem of the regulatory role of proteoglycans in mineralization and in the maturation of mineral and matrix moieties in skeletal tissue.

Salter innominate osteotomy. The effect of blood supply to the roof of the acetabulum

Quantitative studies of blood flow (hydrogen washout technique) and bone mineralization rate (tetracycline labeling) were performed in the ilium of 23 immature dogs before and after Salter innominate osteotomy. The vascular anatomy, blood flow rate, and mineralization rate (appositional bone growth) on the roof of the acetabulum were disturbed after operation. Radiographic healing and normal patterns of circulation to the ilium were partially restored within two weeks and completely restored after six weeks. The data suggest that a single iliac osteotomy is without long-term consequence to the viability of acetabular bone.

Growth and maturation of mandibular bone in otherwise totally immobilized rhesus monkeys

The effects of 14 days of total postcranial body immobilization (in plaster casts) on the mineralization rate and on the maturation of matrix and mineral moieties in the rhesus jaw were studied by tetracycline labeling and by density gradient methods, respectively. Immobilization did not alter the rates of periosteal and endosteal mineralization in the dense cortical bone from the lingular region of the jaw, but it did impair mineralization in osteonal bone. Osteons that continued to show radial closure did so at a normal rate. In the more trabecular cortex (premolar region) in young monkeys (3-6 kg body weight), immobilization impaired bone mineralization, as shown by lower ratios of calcium and inorganic phosphorus to hydroxyproline (Ca/HO-Pr;Pi/HO-Pr), and it reduced the rate at which the newly formed bone and mineral moieties matured. In older monkeys (6-10 kg body weight) immobilization did not alter Ca/HO-Pr and Pi/HO-Pr ratios or impair tissue maturation. These changes tended to normalize within 7 to 14 days after decasting.

Meal timing as a Zeitgeber for skeletal deoxyribonucleic acid and collagen synthesis rhythms

Meal timing protocols were used to probe the circadian regulation of DNA and protein synthesis in the rat tibia. Two groups of 4-week-old rats were entrained to 12-h light, 12-h dark cycles (light, 0800-2000 h; darkness, 2000-0800 h) for 4 weeks. One group was fed for 4 h at the onset of the light span (EL). The other group was fed for 4 h at the onset of the dark span (ED). Forty-eight hours before death, the rats were injected ip with 0.015 microCi/g BW [14C]proline [collagen and noncollagen protein (NCP) synthesis], and they received 0.25 microCi/g BW [3H] thymidine (DNA synthesis) 1 h before death. Groups of 10-12 rats were bled from the abdominal aorta at 4-h intervals under light ether anesthesia (1-2 min/rat) during 2 consecutive 24-h periods, and the tibias were then biopsied and frozen in liquid N2. Serum samples were analyzed for calcium, inorganic phosphorus, and immunoassayable levels of corticosterone (CS), PTH, and calcitonin. Epiphyseal cartilage and metaphyseal and diaphyseal bone were analyzed for DNA and acidic pepsin-digestible collagen. Chronograms indicated that DNA synthesis in cartilage and bone, along with serum CS, showed two approximately equal and positively correlated peaks, with the cycles for rats fed EL vs. ED being in approximate antiphase. The fit of a 12-h cosine curve was statistically significant in all cases (P less than 0.01). The acrophase peaks were: EL, 0800 and 2000 h; and ED, 1600 and 0400 h. These patterns were unrelated to those for NCP and collagen synthesis. EL and ED relationships for NCP synthesis were also antiphasal. A statistically significant circadian rhythm of collagen synthesis was detected in cartilage and bone of ED-fed rats (peak, 0800 h; nadir, 2400 h). In EL-fed rats, the 0800 h peak alone was muted. No consistent correlations were observed between serum calcium and phosphorus chronograms and those of cartilage and bone collagen and DNA synthesis. The results suggest that physiological alterations of CS in vivo serve to modulate cartilage and bone cell proliferation, but they do not seem to regulate the phasing of the net collagen synthetic rhythm.

Simulating certain aspects of hypogravity: effects on bone maturation in the non-weight bearing skeleton

This study reports the effects of simulation of certain aspects of hypogravity (via partial skeletal unloading) on the growth and maturation of the non-weight bearing mandibles of 41-d and 1-yr-old rats. Partial skeletal unloading was effected by elevating the hindquarters (PULEH), and this simulation was controlled with normally loaded animals fed either ad libitum or the average amount of food consumed by the the experimental group (group-mean fed). The chemical status of the mandibles after 10 d or 14 d PULEH closely resembled that of control rats. The younger PULEH rats and their group-mean fed controls demonstrated a trend toward impaired maturation of mineral and matrix moieties; yet the concentrations of calcium (Ca) and phosphorus (P) expressed as a ratio to collagen hydroxyproline content were normally distributed within a density gradient profile which separates the mineral and matrix moieties into various age-dependent fractions. These data demonstrate that 10 d or 14 d PULEH in young or old rats, respectively, is not sufficient to elicit the maturation deficit observed in the mandibles of rats flown for 18.5 d in the Soviet Biosatellite Cosmos-1129. Unless the duration of PULEH is critical, the cephalad fluid shift which is common to PULEH and spaceflight animals cannot be solely responsible for the flight-induced maturation deficit. Because the mandibles of the PULEH rats remain antigravity-postured, the results emphasize the importance of gravity unloading to the impairment of mandibular bone matrix/mineral maturation during spaceflight. Decreased gravity and, hence, gravity unloading cannot be mimicked in ground-based models of hypokinesia.

Healing of canine femoral osteotomies. Effects of compression plates versus Eggers' plates

The effects of rigid self-compressing plates were compared with the effects of less rigid internal contact splints on the healing characteristics of osteotomized canine femora. Radiographically, the rigid fixation afforded by the compression plate produced accelerated healing as compared with the less rigid fixation obtained with splints at two to four months. At six months there was little or no difference between the two groups. Comparison of the material biomechanical properties of the healing femora suggested that the repair tissue formed early after compression plating was stronger than the callus tissue that surrounded the less rigidly fixed femora. A comparison of the structural biomechanical properties of the bones suggested, conversely, that a stronger whole bone resulted from the less rigid fixation splint. The histomorphometric data showed that some cortical bone was lost under both types of fixation plates. However, the patterns of loss were not comparable. Use of rigid internal fixation led to loss of cortical bone after four to six months, while the less rigid fixation obtained with the Eggers splint produced mild intracortical resorption only. These observations point to the desirability of rigid internal fixation early in the healing process and the possible benefit of decreasing the rigidity of the fixation device as healing proceeds.

The effect of protracted tetracycline treatment on bone growth and maturation

Mature female rhesus monkeys were used to evaluate the effects of a one-year course of tetracycline (50 mg/kg/day, intramuscularly) on the formation, maturation, and mineralization of mandibular bone. The bones from the treated group contained normal concentrations of calcium (Ca), inorganic phosphorus (Pi), and hydroxyproline (HO-Pr), and the treatment schedule did not alter the distribution (percentage) of total osteons into slightly, moderately, and highly mineralization classes. Tetracycline impairs bone mineralization and the subsequent maturation of the mineral and matrix moieties. The percentage of highly mineralized osteons labeled with tetracycline is subnormal. Density gradient fractionation studies indicate the presence of abnormally high Ca/Pi ratios in the temporally young newly formed bone mineral and somewhat higher ratios in the most mature bone fraction. Protracted tetracycline treatment at high dosages impairs bone growth and maturation in adult rhesus monkeys.

Effect of spaceflight on the non-weight-bearing bones of rat skeleton

Male Wistar rats prelabeled with tetracycline to mark surfaces of bone and tooth formation-mineralization were placed into orbit for 18.5 days aboard the Soviet COSMOS-1129 Biosatellite. They were injected with tetracycline for a second and third time on the 6th and 27th days, respectively, after recovery of the Biosatellite. Spaceflight did not alter the rate of periosteal bone formation in the non-weight-bearing ribs and regions of the mandibles, which were covered by masticatory muscles. Bone formation-calcification rates were impaired at those sites in the jaw that had no contiguous muscle (molar region). The remodeling activity on the alveolar bone around the buccal roots of the molar teeth was significantly reduced but without creating a negative balance between formative and resorptive activities. Total Ca, P, and hydroxyproline concentrations in the jaws, incisors, and ribs were normal after spaceflight, but gravity density fractionation studies indicated that in the jaws alone, O-G conditions caused a delay in the maturation of bone mineral and matrix. A 29-day postflight recovery period at earth's gravity was sufficient to fully correct these anomalies. Relative to tooth formation, relatively normal circadian and infradian biorhythmic periodicities of Ca and P in dentin and enamel were maintained during spaceflight. We conclude that most of the non-weight-bearing bones of the rat skeleton are at risk to the effects of hypogravity.

Plugged haversian canals and local dose in radium cases

Haversian canal plugging is a common lesion in bone from human radium cases, signaling vascular damage. Its incidence is correlated with the whole body radium dose. However, since the vascular supply to bone forms an extensive anastomotic plexus facilitating propagation of vascular damage from a primary site of high radium content, we do not know if the degree of plugging is related to the local bone dose. In this report, we compare the incidence of plugging of osteons in different regions (16 sections) of humeri of three radium cases with terminal 226Ra body contents of 0.203, 1.03 and 15.4 muCi to the local dose of radium in adjacent bone sections. While the first and third subjects had received 226Ra only, the second had had a large intake of 228Ra as well. The background incidence of plugging in 35 "normal" humeri from dissecting room populations (45-90 yr) ranged from 0 to 1%, with an average of 0.3%. The least squares linear regression equation for the relation between the percent of canals plugged (PCP) and dose, PCP = (0.00214 +/- 0.00014) rad + (3.26 +/- 3.6), predicts for our three radium cases a development of about 0.002% plugs/rad. The correlation coefficient was very high (r = 0.97, n = 16, P less than 0.01). When normalized to radiation dose from the two decay series, 226Ra and 228Ra appear to be equally effective in producing plugged canals.

Formation of bone by isolated, cultured osteoblasts in millipore diffusion chambers

Osteoblast-like and osteoclast-like cells freed from neonatal calvaria by sequential enzymatic digestion after 6-7 days in culture were placed in diffusion chambers and implanted in the peritoneal cavities of CD-1 mice. About half of the chambers also contained a dead calvarium to test for the need of an "inducer." After 20 days, 11 of 18 chambers containing to osteoblast-like cells formed large foci of mineralized bone that corresponded to alkaline phosphatase activity throughout the chambers. Moreover, only type I (i.e., bone) collagen was formed. Occasional deposits of bone were found in only 3 of 22 chambers containing the osteoclast-like cells. The presence of dead bone did not affect any of the results. These data confirm the osteoblast-like nature of the isolated cell populations and demonstrate that these cells retain their differentiated function in culture.

A cellular investment of bone marrow

We describe a method for clearly separating the cell layers at the bone-marrow interface, which reveals that the myeloid tissue is invested by an epithelial-like layer of specialized squamous cells we call the marrow sac. The scanning electron microscope showed that the sac was fenestrated and that some of its cells pass as perivascular elements with the marrow capillaries that penetrate the bony cortex. The transmission electron microscope (TEM) showed that the cells comprising the marrow sac are less than 0.1 micrometer thick, overlap at their margins without specialized cell junctions, and are more electron dense than the reticular or fibroblastic cells of the marrow stroma. The fenestrations in the sac were intercellular and were usually occupied by cells having an ultrastructure compatible with an osteoprogenitor cell (OPC) lineage. The observation of a close proximity between the cells of the marrow sac and the osteogenic cells that line the endosteal surfaces of bone suggest that the sac cells, along with the OPCs of the superficial marrow stroma, should be included in any morphological or functional definition of an endosteum.

Articular cartilage repair in the avian quail-chick chimera model

The natural history of the cells which participate in the repair of defects in articular cartilage was studied in the chick-quail chimeric system. This system involves interspecific grafting of quail limb rudiments onto the vascularized chick embryo chorioallantoic membrane (CAM) where the grafts revascularized and grow. Differences in cell morphology make it possible to clearly differentiate cells which subsequently arise from the grafted elements, from those which subsequently originate in the host (chick) tissues and migrate into the grafts. Herein, lesions were produced in quail femurs just prior to the time they were grafted to the chick CAM. The lesions were of two types: those restricted to the proliferative and hypertrophic zones of the cartilaginous epiphyses, and those which penetrated through the cartilage into the subchrondral marrow space. Epiphyses cut transversely at the level of the proliferative and hypertrophic cells failed to resurface with hyaline cartilage or fibrocartilage. Cavities produced in these areas also failed to repair. However, lesions which penetrated through the epiphyses into the medullary spaces filled with calcified bone trabeculae, and all the osteoblasts and osteocytes in the repair bone had nuclei of the graft (quail) type. The observations suggested that the cells resident in articular cartilage have little ability to effect healing, and that the new bone was derived from osteoprogenitor cells in the quail marrow stroma which moved with capillaries into the lesions. Indirect evidence is presented to support the concept that chondrocytes surviving ossification of the epiphyses can also contribute to the osteoprogenitor cell pool. A fibrocartilage metaplasia was not observed at the joint surface in this system, presumably due to the absence of biomechanical influences.

Salmonella livingstone salmonellosis in laboratory mice: successful containment and treatment of the disease

An outbreak of fatal enteritis in CBA/ca mice, associated with Salmonella livingstone, was successfully treated by administration of tetracycline in drinking water together with careful observation of hygienic routines.

Altered metabolic rhythm of rabbit osteoblasts by tetracycline

To establish whether there are single or multiple pools of osteoblasts in rabbit bone, animals were injected with tetracycline on various schedules for 1-3 days. Metabolic restraints predicted that a multiple pool model would be feasible only if the percent labeled surfaces of trabecular bone (tibia) doubled when animals were injected on days 1 and 2, 1 and 3, or on days 1, 2, and 3. A single population would be indicated if the extent of labeled surfaces failed to double. Herein, 41.9 +2- 8.1% of bone surfaces labeled after a single injection, and only 60-68% of surfaces labeled after injections on the other schedules. The data inferred tht serial pulse tetracycline injections at 24h intervals caused a shift in the activities of a single population of osteoblasts and their progenitor cells.

Salmonella montevideo salmonellosis in laboratory mice: successful treatment of the disease by oral oxytetracycline

In an epidemic outbreak of salmonellosis associated with Salmonella montevideo in 6 mouse colonies, most deaths occurred in BALB/c and ASI mice, although the carrier rate was similar in other mouse strains. The salmonella was eradicated from ASI mice of 4-6 weeks old, and the carrier rate considerably reduced at 12-26 weeks of age, by use of oral oxytetracycline in conjunction with strict hygiene measures. Housing mice on wire grids instead of wood shavings did not affect the efficacy of the treatment.

Postfracture linear bone growth in rats: a diurnal rhythm

The effect of fracture of the tibia on the subsequent overgrowth of the femur in the injured limb has been studied in ad lib, -fed rats. The thrust of these studies was to determine if the time in the body rhythm (diurnal) when injury was sustained could influence the rate of postfracture linear bone growth. Accordingly, different groups of young rats were subjected to tibial fracture at one of 4 times in a 24 hour day (6 hours apart), and a ratio of femur lengths (injured left side/intact right side) in each group was calculated 30 days thereafter. The data indicated that midday was the only time when tibial fracture elicited significant femoral overgrowth. At this time, the femur length differential in the fractured rats was small (0.52 mm), but it was significantly greater than that observed in intact control rats. The diurnal response was not present in fractured hypophysectomized rats, nor could it be detected in normal rats by measuring the thicknesses of the growth cartilages from the intact and fractured tibias. However, in 2 separate studies, the patterns of radiostrontium retention in the tibias and in the femurs confirmed that midday was the time in the rat body rhythm when processes of ossification in the epiphyses and in the remodeling fracture callus proceeded most actively. The 24-hour retention of 85Sr in the fractured tibias was greater than that in the intact tibias (5 days postfracture), but the 5-day retention of isotope in the femurs on the side of tibial fracture (30 day postfracture) was significantly less than that of the bone in the uninjured limb. The skeletal responses to fracture are not limited to the injured element; the magnitude of the responses both in injured and intact bones of a limb have a diurnal component.

Observations on the host specificity of Hymenolepis straminea (Goeze)

The experimental infection of rodents as potential, definitive hosts with Hymenolepis straminea indicated that hamsters and field mice were susceptible to infection. By comparison, laboratory mice exhibited a significantly lowered susceptibility. Artificially induced depression of the immune response enabled the parasite to be cultured in several strains of laboratory mice, and suggested that the thymus played a major role in rejection of the parasite.

Two Actinobacillus species isolated from laboratory rodents

A study was made of the cultural and biochemical characteristics of 17 strains of Actinobacillus isolated from laboratory rats and hamsters. 2 types were recognized which differed in their urease reaction and colony colour on blood agar. The results obtained suggest that one was Actinobacillus equuli but the other could not be identified as belonging to a described species. The characteristics of both organisms are such that they could be confused with Pasteurella pneumotropica. One of the types was isolated from tapwater.