Active oxygen radicals produced by leukocytes of malignant lymphoma

The electron spin resonance (ESR) spectra of active oxygen radicals produced during the respiratory burst of PMA-stimulated leukocytes and oxygen consumption are studied by ESR spin trapping and spin probe oxymetry for 31 times in 17 cases of malignant lymphoma. The results showed that the spectra produced from PMA-stimulated patients' leukocytes were predominantly spin adducts of DMPO-hydroxyl radicals (DMPO-OH). The decrease in oxygen consumption during respiratory burst suggested that respiratory burst function was inhibited. Kinetic observations of patient condition showed that respiratory burst and oxygen consumption were improved and even approached normal, when the patient was in remission or the condition was ameliorated. This paper is the first of its type and helps clarify the mechanism of malignant proliferation and metastasis.

Detection of free radical scavenging activity of schisanhenol by electron spin resonance

It was reported that Schisanhenol (Sal) isolated from Schisandrae Rubriflora inhibited lipid peroxidation induced by ferrous-cysteine and NADPH-ascorbic acid. In this studies the oxygen radical scavenging activity of Sal was detected by electron spin resonance (ESR) and spin trapping. Sal was shown to scavenge oxygen radicals produced by human neutrophils (Neu) stimulated by tetradecanoylphorbol acetate (TDPA). But no effect of Sal was seen on oxygen consumption measured by spin label oximetry in Neu during respiratory burst. In Fenton reaction system, the inhibitory rate of hydroxyl radical by Sal was 34.4%. In xanthine-xanthine oxidase and uv-irradiation of riboflavin systems, Sal scavenged superoxide anion radical by 26.1% and 21.9%, respectively. In all these systems the action of Sal was more potent than that of vitamin E. It may be concluded that Sal possesses a free radical-scavenging activity.

[Scavenging effects of sodium ferulate and 18 beta-glycyrrhetic acid on oxygen free radicals]

The scavenging effects of sodium ferulate (SF) and glycyrrhetic acid (GA) on oxygen free radicals were studied by using spin trapping technique and chemiluminescence (CL) methods. SF 0.3 mmol/L and GA 0.3 mmol/L effectively scavenged oxygen free radicals produced by phorbol myristate acetate (PMA)-stimulated polymorphonuclear leukocytes (PMN), but had no effect on the oxygen consumption by PMN, measured with spin probe oxymetry. In 3 cell-free oxygen free radical generating systems, both SF and GA showed a remarkably scavenging effects on O2- and OH.. SF 30 mumol/L and GA 30 mumol/L prominently inhibited the CL response of PMA-stimulated PMN. The results demonstrated that SF and GA are oxygen free radical scavengers.

Adaptation of cancellous bone to overloading in the adult rat: a single photon absorptiometry and histomorphometry study

Nine-month-old female rats were subjected to right hindlimb immobilization or served as controls for 0, 2, 10, 18, and 26 weeks and were double-labeled with bone markers. The right limb was immobilized against the abdomen and considered unloaded, while the left limb was overloaded during ambulation. Single-photon absorptiometry was performed on intact femur; static and dynamic histomorphometry were performed on 20 microns thick undecalcified frontal sections of the proximal tibial metaphysis. Changes in the continuously overloaded limb was compared to that in both limbs of age-matched control animals. Single-photon absorptiometry detected increases of bone mineral density of +6%, +6%, and +5% in the proximal and +9%, +7%, and +10% in the distal femoral metaphyses after 10, 18, and 26 weeks of continuous overloading. Morphometrically, significant changes occurred in proximal tibial metaphyses compared to age-matched controls: trabecular area increased +41% and +45%, trabecular number increased +31% and +32%, and trabecular separation decreased -30% and -31% after 18 and 26 weeks of overloading. A significant increase in mineral apposition rate (+38%) was found only at 26 weeks of overloading. Insignificant decreases in both eroded and labeled bone surfaces occurred at all time periods. The histomorphometric changes indicated that increased cancellous bone mass was caused by an increase in bone formation activity (i.e., increases in mineral apposition and bone formation rates) and a decrease in remodeling space (i.e., decrease in bone eroded surface). These findings indicate that the adult skeleton can quickly adapt to the increased biomechanical needs by increasing its cancellous bone mass with an adequate structural pattern.(ABSTRACT TRUNCATED AT 250 WORDS)

Scavenging effect of berbamine on active oxygen radicals in phorbol ester-stimulated human polymorphonuclear leukocytes

The scavenging effect of berbamine (Ber) on active oxygen radicals was studied, using a spin-trapping technique and a chemiluminescence (CL) method in phorbol myristate acetate (PMA) stimulated polymorphonuclear leukocytes (PMN) and in four cell-free superoxide (O2-.) or hydroxyl radical (OH.) generating systems. Ber (0.1 to 0.3 mM) effectively reduced active oxygen radicals in PMN stimulated with PMA, but had no obvious effect on oxygen consumption during the respiratory burst of PMN, measured with spin probe oxymetry. Ber (0.3 mM) prominently inhibited the CL response of PMA-stimulated PMN. The agent remarkably quenched O2-. in xanthine/xanthine oxidase and irradiation riboflavin systems and OH. in the Fenton reaction. Its scavenging action on O2-. was stronger than that of Vitamin E in the xanthine/xanthine oxidase system but the same as Vitamin E in the riboflavin system, and its action on OH. was similar to that of Vitamin E.

Adaptation of cancellous bone to aging and immobilization in the rat: a single photon absorptiometry and histomorphometry study

Nine-month-old female rats were double-labeled with bone markers and subjected to right hindlimb immobilization or served as control for 0, 2, 10, 18, or 26 weeks. The right limb was immobilized against the abdomen, thus unloading it, while the left limb was overloaded during ambulation. Single photon absorptiometry and cancellous bone histomorphometry were performed on dissected intact femur and 20-microns-thick undecalcified specimens of the proximal tibial metaphysis. In the unloaded limb, immobilization-induced muscle and cancellous bone loss occurred rapidly before 10 weeks and stabilized at 50% less bone mass after 18 weeks. Unloading caused a negative bone balance from a combination of elevated bone resorption and depressed bone formation. At 2, 10, and 18 weeks of immobilization, the ratios of bone resorption to bone formation surfaces were 1.6, 1.5, and 1.3, respectively; at 26 weeks, the ratio was 1. The bone loss was accompanied by poorer trabecular architecture (trabecular number decreased and trabecular separation increased), reaching the maximum at 18 weeks and stabilizing thereafter. These observations are in general agreement with Frost's postulate for mechanical effects on lamellar bone remodeling, and the findings on disuse osteoporosis in man. Therefore, the one-legged immobilization model can be useful in studies of the mechanisms of structural adaptation to mechanical usage.

[Anti-arrhythmic effects of matrine]

Matrine (MT) is an alkaloid isolated from Sophra alopecuroids L. The LD50 of MT iv to mice was 72.1 mg/kg (95% CL 68.2-76.5 mg/kg). MT had significant effects on different experimental models of arrhythmias induced by aconitine, barium chloride or coronary ligation. The ECG of anesthetized rats was significantly changed after iv of MT. The HR was retarded and the PR and QTc intervals were prolonged.

Scavenging effect of schizandrins on active oxygen radicals

The reactive oxygen radicals produced from human polymorphonuclear leukocytes (PMN) stimulated with PMA (phorbol myristate acetate), hydroxyl radicals generated by a Fenton reaction, and superoxide anion radicals produced by irradiating solutions of riboflavin in the presence of EDTA have been taken as the models for production of oxygen radicals. With the use of the electron spin resonance spin trapping method, the scavenging effects of schizandrol A (solA) (5 x 10(-4) M) and schizandrin B (sinB) (5 x 10(-4) M) have been studied and compared with the effects of vitamin E (5 x 10(-4) M) and vitamin C (5 x 10(-4) M). It has been found that in cell system the scavenging effects of sinB and solA, as judged by ESR spin trappings, on hydrpxyl radicals (.OH) are greater than vitamin E and vitamin C and the scavenging effects on superoxide anion (O2) are greater than vitamin E but lower than vitamin C. With respect to the Fenton reaction, sinB has the strogest scavenging effect on .OH (77%) and solA has strong scavenging effect on .OH (63%), both of them larger than that of vitamin E (35%) and vitamin C (56%). In the riboflavin/EDTA system, the scavenging effect of sinB (46%) is smaller than that of vitamin C (96%) but larger than that of vitamin E (23%); the scavenging effect of solA is not obvious (14%). With the use of spin probe oximetry, the oxygen consumption during the respiratory burst of stimulated PMN has been measured when exposed to schizandrins. The experiment results demonstrated that they do not affect the activity of production of active oxygen radicals in the respiratory burst of PMN stimulated with PMA.

Transient effects of subcutaneously administered prostaglandin E2 on cancellous and cortical bone in young adult dogs

The transient effects of prostaglandin E2 (PGE2) on cancellous and cortical bone in iliac crests and mid-tibial shafts of nine intact young adult dogs were evaluated following 31 days of treatment. Histomorphometric bone changes were characterized from in vivo fluorescent double-labeled undecalcified bone specimens. PGE2 caused an increase in cancellous bone remodeling evidence by increased in activation frequency; increased percent eroded and formation surfaces; increased mineral apposition and bone formation rates; and shortened resorption, formation, and total bone remodeling periods. Activated cancellous bone remodeling did not lead to decreased cancellous bone mass, indicating an imbalance between bone resorption and formation in favor of formation (activation----resorption----stimulated formation; A----R----F increases) at remodeling sites. The PGE2 treatment activated bone modeling in the formation mode (activation----formation; A----F) at the periosteal and endocortical surfaces and increased activation frequency of intracortical bone remodeling in the tibial shaft. Increased modeling activation converted quiescent bone surfaces to formation surfaces with stimulated osteoblastic activity (i.e., increased percent labeled periosteal and endocortical surfaces, mineral apposition rates, and woven and lamellar trabecular bone formation) leading to 9- to 26-fold increases in newly formed bone mass in subperiosteal, subendosteal, and marrow regions, compared to controls. However, increased intracortical bone remodelling elevated remodeling space (i.e., increased cortical porosity), producing a bone loss that partially offsets the bone gain. The combined events lead to a positive bone balance in PGE2-treated cortical bone, compared to a negative bone balance in control bones. Collectively our data suggest that in vivo PGE2 is a powerful activator of cancellous and cortical bone formation, which may be able to build a peak bone mass to prevent and/or correct the skeletal defects to cure osteoporosis.

Prostaglandin E2 enhances cortical bone mass and activates intracortical bone remodeling in intact and ovariectomized female rats

To assess the efficacy of prostaglandin E2 (PGE2) in augmenting cortical bone mass, graded doses of PGE2 were subcutaneously administered for 30 days to seven-month old sham-ovariectomized (SHAM) and ovariectomized (OVX) rats. Both groups were operated at three months of age. Histomorphometric analyses of double fluorescent labeled tibial shafts were performed on basal control, OVX, and SHAM rats treated with 0, 0.3, 1, 3, and 6 mg PGE2/kg/d for 30 days. Baseline aging data showed increased cortical tissue and cortical bone area and reduced bone formation parameters at the periosteal and endocortical bone envelopes between three and eight months of age. The tibial shafts of OVX rats compared to SHAM controls showed elevated periosteal mineral apposition rate and endocortical bone formation parameters. PGE2 administration to OVX and SHAM rats increased cortical bone by the addition of new circumferential bone on the endocortical and periosteal surfaces, as well as woven cancellous bone in the marrow region. Stimulated osteoblastic recruitment and activity enhanced bone formation at all bone surfaces. The new bone was both lamellar and woven in nature. PGE2 treatment also activated intracortical bone remodeling (not seen in untreated eight-month old rats), creating a porous cortex. Thus, PGE2 administration activated cortical bone modeling in the formation mode (A----F), as well as intracortical bone remodeling (A----R----F). PGE2 administration to OVX rats resulted in more intracortical bone remodeling, periosteal bone formation, and new cancellous bone production than observed in PGE2 treated controls. The findings that PGE2 administration to OVX and intact female rats increases cortical bone mass, coupled with observations that mouse, rat, dog, and man respond similarly to PGE2, suggest that PGE2 administration may be useful in the prevention and treatment of postmenopausal osteoporosis.

Scavenging effects on active oxygen radicals by schizandrins with different structures and configurations

We have studied the scavenging effects of different structures and configurations of schizandrins isolated from Fructus Schizandrae, a traditional Chinese herb, on active oxygen radicals with the method of spin-trapping technique. The active oxygen radicals were produced from human polymorphonuclear leukocytes (PMN) stimulated with phorbol myristate acetate (PMA). In addition, the scavenging effects of schizandrins on hydroxyl radicals (.OH) in Fenton's reaction and the scavenging effects on superoxide anions (O2-.) in both riboflavin/EDTA and xanthine/xanthine oxidase systems have also been studied. They are compared with the scavenging effects of both Vitamin C (Vc) and Vitamin E (VE). The experimental results have shown that the scavenging effect of schizandrin B (Sin B) on the active oxygen radicals is stronger than that of S(-) Sin B and R(+) Sin B. For schizandrins of the same molecular structures with different stereoconfigurations the scavenging effects of S type of the benzene ring on active oxygen radicals are stronger than those of R type and for schizandrins of the same stereoconfigurations with different structures the scavenging effects of schizandrin C (Sin C) on the active oxygen radicals are stronger than those of Sin B.

Effects of prostaglandin E2 on production of new cancellous bone in the axial skeleton of ovariectomized rats

The effects of prostaglandin E2 (PGE2) were histomorphometrically evaluated in cancellous bone of the axial skeleton of ovariectomized, osteopenic rats. Four months following bilateral ovariectomy (OVX) and sham-ovariectomy (SHAM) at 3 months of age, rats received daily subcutaneous injections of PGE2 at 0, 0.3, 1.0, 3.0 and 6.0 mg/kg/day for 30 days. The undecalcified fourth lumbar vertebral bodies (LVB) were processed for static and dynamic bone histomorphometry. The OVX rats possessed a slightly osteopenic LVB (17% vs. 24% cancellous bone mass). In rats given PGE2 at 3 and 6 mg/kg/day for 30 days, bone turnover, lamellar bone mass, and formation of new woven bone trabeculae were increased. Observations supported the conclusion that PGE2 activates bone modeling and remodeling, and shifts bone balance in favor of formation. In OVX rats given 6 mg PGE2/kg/day, cancellous bone mass and trabecular numbers were restored to levels found in untreated SHAM rats. Cancellous bone mass in the LVB of SHAM rats given 3 and 6 mg PGE2/kg/day increased by 16% and 30% over that of control rats. In addition, PGE2 stimulated longitudinal bone growth in both OVX and SHAM rats, a response that differed from male rats.

Estimation of pubic age among Chinese Han people by means of multiple stepwise progressive analysis

This paper sets up an equation for estimating male and female ages separately by means of a computer with mathematical model of multiple stepwise progressive regression on data of 454 pairs of pubes of Chinese Han people in Northeast China. The equation upgrades a standardization of pubic age estimation to quantification. The correlation coefficient of the equation is 0.9906-0.9912; S.D. is 1.56-1.97; variance analysis F greater than 001 and p less than 0.01. By a blindfold test of 43 pairs of pubic bones with birthdate, the rate of concordance is 76-82% for +/- S.D. and 92-96% for +/- 2S.D.

[Scavenging effects of probimane on active oxygen free radicals by electron spin resonance]

Probimane, dl-1,2-bis (4-morpholine-methyl-3, 5-dioxopiperazin-1-yl) propane, is a new antitumor agent synthesized by Shanghai Institute of Materia Medica, Chinese Academy of Sciences. The scavenging effects of probimane on active oxygen radicals produced in 3 different systems were studied with the ESR spin trapping methods. In Fenton's reaction, probimane remarkably scavenged hydroxyl radicals (.OH) and the rate of scavenging .OH by probimane 0.05 mmol/L was 47%, compared to 5% by vitamin E (VE) and 30% by ascorbic acid (AA). In irradiation riboflavin system, in which superoxide (O2-.) was produced, the agent also had the scavenging effects on O2(-.). The rate of scavenging O2-. by probimane 0.05 mmol/L was 13%, higher than that by VE (7%) but lower than that by AA (90%). In cell system where the active oxygen radicals were produced during the respiratory burst of human neutrophils (Neu) stimulated by TPA (tetradecanoylphorbol acetate), probimane exhibited a dose-dependent scavenging action on the radicals. The rate of the radical scavenging by probimane 0.05 mmol/L was 37%, much higher than that by VE (9%) but lower than that by AA (68%). Probimane had no effect on the rate of oxygen consumption by human Neu, measured with spin probe oxymetry.

The effects of chronic vitamin A excess on bone remodeling in aged rats

This study was conducted to assess the effects of long-term ingestion of moderate excesses of vitamin A on trabecular bone remodeling in the fifth lumbar vertebral body of aged rats. Eighteen-month-old rats were fed diets with vitamin A content equal to the daily requirement (DR), 2-fold, and 5-fold the DR along with calcium content of either the DR or 0.3-fold the DR, for 14 months each. As expected, serum concentrations of 1,25-dihydroxyvitamin D were higher in the reduced than in the normal calcium intake groups (65.1 +/- 2.4 SEM vs 47.8 +/- 2.1 pg/ml, P less than 0.001). Calcium balance was more positive at the higher than the lower calcium intake (5.7 vs 0.9 mg, P less than 0.001) but was unaffected by vitamin A intake. Histomorphometric analysis of the fifth lumbar vertebral body revealed that the 2-fold but not the 5-fold excess in vitamin A intake resulted in a 15% increase in percentage of trabecular bone (P less than 0.02). The low calcium diet depressed bone growth (total bone tissue) but did not affect percentage of trabecular bone. Several effects of the vitamin A excess and low calcium diet were noted along the trabecular surface including increased mineral apposition rate and resorption surfaces and decreased formation surfaces. The net effect of vitamin A on trabecular bone of the rat varies as intake begins to exceed the DR. At a 2-fold excess, a modest favorable effect on percentage of trabecular bone was observed.

ESR studies on active oxygen radicals produced in the respiratory burst of human polymorphonuclear leukocytes

The mechanism and process of production of active oxygen radicals in the respiratory burst of polymorphonuclear leukocytes (PMN) stimulated with PMA (phorbol myristate acetate) was studied in this paper. The experimental results indicate that when the PMA was dilute enough or at the beginning of stimulation even when the PMA concentration was high, the spectrum of hydroxyl radical spin adducts, DMPO-OH, was dominant in the ESR spectra. However, at the maximum level of the respiratory burst, the spectrum of superoxide anion spin adducts, DMPO-OOH, was dominant.

ESR studies on oxygen consumption during the respiratory burst of human polymorphonuclear leukocytes

Oxygen consumption during the respiratory burst of human polymorphonuclear leukocytes (PMN) stimulated with phorbol myristate acetate (PMA) was studied with spin probe oxymetry and using the transition metal ion CrOX (potassium trioxalatochromate) as a widening agent. The experimental results demonstrated that during the respiratory burst of PMN stimulated with PMA, oxygen consumption was found mainly in the intercellular medium but no change of oxygen concentration was found in the intracellular medium.

Scavenging effect of extracts of green tea and natural antioxidants on active oxygen radicals

With the use of the spin trapping methods, the scavenging effects of the extracts of green tea and other natural foods are studied. In stimulated polymorphonuclear leukocytes (PMN) system, water extract fraction 6 (F6) from green tea and green tea polyphenols (GTP) have the strongest scavenging effect on the active oxygen radicals, much stronger than vitamin C (Vc) and vitamin E (VE). Rosemary antioxidants (RA) and Curcumin (Cur) have weaker scavenging effects than Vc, but stronger than VE. In Fenton Reaction, Cur has the strongest scavenging effect (69%) on hydroxyl radicals. In irradiation, riboflavin system F6(74%) and GTP(72%) have very strong scavenging effects that are weaker than Vc, but much stronger than VE (23%). With the use of spin probe oxymetry, the oxygen consumption in respiratory burst of stimulated PMN were measured when the antioxidants existed in these systems. The results demonstrated that these antioxidants did not affect the respiratory burst of human polymorphonuclear leukocytes stimulated with PMA.

[Clinical observation on hypercortisolism treated with amino-glutethimide]

We reported the clinical results in 13 cases of hypercortisolism treated with amino-glutethimide (AG), which was developed by Tiantsin Research Institute of Medical Industry. Of the thirteen cases nine were confirmed by surgery and histology, and the others were diagnosed clinically. Clinical improvements have been achieved in ten of the thirteen cases over a therapeutic course of 8 to 12 wk with a daily dosage of 1.0 to 2.0 g of AG. Plasma and urinary corticosteroids, as well as plasma testosterone levels were significantly decreased after one-month treatment followed, however, by somewhat return and fluctuation. The high levels of blood glucose and serum insulin were declined after therapy consistent with the decrement of corticoids. Serum potassium levels in hypokalemic patients returned to normal after one month of therapy. Radial bone mineral contents in patients with low bone density returned or closed to normal after three-month treatment. The main side effects of AG are anorexia, nausea, drowsy, tierdness, skin rashes, etc, which are mild and transient. Adrenal hypofunction was seen in one case after treatment.

Flurbiprofen enhances growth and cancellous and cortical bone accumulation in rapidly growing long bones

The effects of flurbiprofen, a non-steroidal anti-inflammatory drug, on bone growth was studied by static and dynamic histomorphometry in immature (28 days old) male Sprague-Dawley rats. Flurbiprofen at 0, 0.02, 0.1, 0.5 or 2.5 mg/kg/d doses was given subcutaneously daily for 21 days. The 0.1 and 0.5 mg/kg/d doses were most effective in stimulating longitudinal and radial bone growth and enhancing the accumulation of cancellous and cortical bone. Proximal tibial longitudinal bone growth rate, growth plate thickness, and periosteal bone formation rate were increased 30-40%, while cortical bone (tibial shaft) and cancellous bone (proximal tibial metaphysis) accumulated 12% and 90% more bone than controls, respectively. Enhanced accumulation of cortical bone was attributed to stimulated periosteal bone formation without accompanying marrow cavity enlargement. Enhanced accumulation of cancellous hard tissue was postulated to be due to reduced trabecular bone resorption and no effect on bone formation. The cell counts support these conclusions. There was a decrease in osteoclast numbers (-62 to -70%), an insignificant decrease in osteoblast numbers (-5 to -30%) per mm of bone surface and a decrease in osteoclast to osteoblast ratio (-35 to -56%). The findings presented are compatible with the conclusion that flurbiprofen, induced changes in rapidly growing long bones by reducing osteoclast activity and recruitment, stimulating longitudinal and radial growth, increasing the cortical bone mass by stimulated periosteal bone growth and depressed endosteal resorption, and increasing cancellous bone mass by depressed trabecular bone resorption without affecting bone formation.

Effects of N,N,N',N'-ethylenediaminetetramethylene phosphonic acid on cortical bone remodeling in the adult dog

Phosphonic acids are of interest because of their potential usefulness in the treatment of disorders of bone and mineral metabolism, as a treatment for dental calculus, and as skeletal imaging agents. The effects of oral doses of N,N,N',N'-ethylenediaminetetramethylene phosphonic acid (EDITEMPA) on cortical bone remodeling and histology of adult dogs were determined. After treatment for 3 and 6 months, there were dose-related changes observed in cortical bone as measured using histomorphometric methods. With higher doses, EDITEMPA treatment resulted in the accumulation of osteoid due to impaired or delayed mineralization of bone. There was an increased mineralized and osseous tissue porosity suggesting an early increase in bone resorption perhaps due to an increased activation of bone remodeling.

Skeletal tissue responses to thermal injury: an experimental study

Skeletal changes occurring secondary to burn injuries were studied in an experimental animal model for thermal injury. One hindlimb of female Sprague-Dawley rats (200-250g) was subjected to a standardized thermal injury; the other hindlimb was left untreated. Control animals received no experimental treatment. Effects on skeletal architecture were studied at the proximal tibial metaphysis and tibial diaphysis using static histomorphometry. Bone formation dynamics were studied from a series of bone fluorochrome labels administered before the experiment began, early (days 8, 9) postburn treatment (PBT) and late PBT (days 17, 18). Animals were sacrificed on day 21 PBT. In proximal tibial metaphyses of burn-treated limbs, trabecular bone area (TBA) and trabecular number in all regions except the primary spongiosa, were significantly reduced. TBA was also decreased, but not significantly in nontreated limbs. Longitudinal growth rate, growth plate thickness and growth cartilage cell production rate are greater in burn-treated than in nonburned and control bones. Burn-treated diaphyses showed extensive woven bone formation at periosteal surfaces, and corresponding increases of bone areas and periosteal perimeters. Endocortical surfaces showed only typical occasional resorption areas. No intracortical changes were observed. Mineral appositional rate (MAR) and bone formation rate (BFR) at endocortical surfaces were markedly depressed after thermal injury, significant changes were noted in both limbs of treated animals. Among burned limbs, the early PBT label was absent from all specimens, indicating a virtual shutdown of osteoblast activity and recruitment. Similarly in nonburned limb bone, the label was absent from 50% of the specimens; in those bones in which the label was present, label lengths, appositional and bone formation rates were significantly reduced relative to the control specimens. Comparison of average bone formation dynamics for the total PBT interval indicates that MAR and BFR in burned treated tibiae were reduced to approximately 25% of control values. MAR and BFR from the nonburned side of treated animals were significantly reduced as well, to about 55% of control values. These data indicate that the principal metaphyseal effects of thermal injury are stimulation of growth cartilage proliferation, and depression of ossification and osteoblast activity. In diaphyses, thermal injury causes extensive local periosteal woven bone proliferation and a dramatic depression of endosteal bone formation. The latter effect, while more severe locally, is also evident systemically.