Diminished bone formation during diabetic fracture healing is related to the premature resorption of cartilage associated with increased osteoclast activity.

Histological and molecular analysis of fracture healing in normal and diabetic animals showed significantly enhanced removal of cartilage in diabetic animals. Increased cartilage turnover was associated with elevated osteoclast numbers, a higher expression of genes that promote osteoclastogenesis, and diminished primary bone formation. INTRODUCTION: Diminished bone formation, an increased incidence of nonunions, and delayed fracture healing have been observed in animal models and in patients with diabetes. Fracture healing is characterized by the formation of a stabilizing callus in which cartilage is formed and then resorbed and replaced by bone. To gain insight into how diabetes affects fracture healing, studies were carried out focusing on the impact of diabetes on the transition from cartilage to bone. MATERIALS AND METHODS: A low-dose treatment protocol of streptozotocin in CD-1 mice was used to induce a type 1 diabetic condition. After mice were hyperglycemic for 3 weeks, controlled closed simple transverse fractures of the tibia were induced and fixed by intramedullary pins. Histomorphometric analysis of the tibias obtained 12, 16, and 22 days after fracture was performed across the fracture callus at 0.5 mm proximal and distal increments using computer-assisted image analysis. Another group of 16-day samples were examined by microCT. RNA was isolated from a separate set of animals, and the expression of genes that reflect the formation and removal of cartilage and bone was measured by real-time PCR. RESULTS: Molecular analysis of collagen types II and X mRNA expression showed that cartilage formation was the same during the initial period of callus formation. Histomorphometric analysis of day 12 fracture calluses showed that callus size and cartilage area were also similar in normoglycemic and diabetic mice. In contrast, on day 16, callus size, cartilage tissue, and new bone area were 2.0-, 4.4-, and 1.5-fold larger, respectively, in the normoglycemic compared with the diabetic group (p < 0.05). Analysis of microCT images indicated that the bone volume in the normoglycemic animals was 38% larger than in diabetic animals. There were 78% more osteoclasts in the diabetic group compared with the normoglycemic group (p < 0.05) on day 16, consistent with the reduction in cartilage. Real-time PCR showed significantly elevated levels of mRNA expression for TNF-alpha, macrophage-colony stimulating factor, RANKL, and vascular endothelial growth factor-A in the diabetic group. Similarly, the mRNA encoding ADAMTS 4 and 5, major aggrecanases that degrade cartilage, was also elevated in diabetic animals. CONCLUSIONS: These results suggest that impaired fracture healing in diabetes is characterized by increased rates of cartilage resorption. This premature loss of cartilage leads to a reduction in callus size and contributes to decreased bone formation and mechanical strength frequently reported in diabetic fracture healing.     

Post-translational processing of the natural human thyrotropin receptor: demonstration of more than two cleavage sites.

Epitope-mapped monoclonal and polyclonal antibodies to the TSH receptor (TSHR) were used as immunoblot probes to detect and characterize the molecular species of the receptor present in normal human thyroid tissue. In reduced membrane fractions, both full-length (uncleaved) holoreceptor and cleavage-derived subunits of the holoreceptor were detected. Uncleaved holoreceptor species included a nonglycosylated form of apparent molecular mass 85 kDa and two glycosylated forms of approximately 110 and 120 kDa. The membranes also contained several forms of cleavage-derived TSHR-alpha and TSHR-beta subunits. TSHR-alpha subunits were detected by antibodies to epitopes localized within the amino terminal end of the TSHR ectodomain and migrated diffusely between 45-55 kDa, reflecting a differentially glycosylated status. TSHR-beta subunits were detected by antibodies to epitopes within the carboxyl end of the TSHR ectodomain. Several species of TSHR-beta subunit were present, the most abundant having apparent molecular masses of 50, 40, and 30 kDa. These data demonstrated that post-translational processing of the TSHR in human thyroid tissue involved multiple cleavage sites.     

059Effects of Two Topical Antimicrobial Agents on Staphylococcus Aureus Biofilms in a Porcine Model

Biofilms are a combination of microorganisms and extrapolysaccharide matrices. Our laboratory has previously demonstrated that biofilms are present in both acute and chronic wounds. Once biofilms are established, phagocytosis and diffusion of antibiotics are impaired thus contributing to antimicrobial resistance due to increased bacterial virulence. The purpose of this study was to determine the efficacy of two topical antimicrobial agents on partial thickness wounds containing Staphylococcus aureus biofilms. All wounds were inoculated with 10⁶ CFU/ml and covered for 48 hrs under a polyurthene film to promote biofilm formation. Wounds were divided into three treatment groups; triple antibiotic ointment (Polymyxin B sulfate, bacitracin zinc, neomycin), mupirocin cream and untreated control. Wounds were treated twice daily. Wounds were cultured for bacterial quantitation at 24, 48, 72, 96, and 120 hrs. Significant reduction in CFU/ml was observed only after several days of treatments. This finding supports the antimicrobial resistance that occurs when bacteria live within biofilms. Our previous studies demonstrated that both of these agents were able to completely eliminate planktonic S. aureus(10⁶) at the early time points. This study demonstrates that when bacterial biofilms are established in wounds there is a longer response time for topical antimicrobial activity suggesting bacterial resistance.     

Bilateral bifid mandibular condyles. Report of three cases

Bilateral bifid mandibular condyles are a rare anomaly that had previously been described only by Hrdlicka in material from skull collections. We present here three cases of bilateral bifid mandibular condyles in patients who sought treatment for other reasons. The radiographic appearance of this anomaly and its embryology are discussed.     

The effect of flow arrest on distal embolic events during arterial occlusion with detachable coils: a canine study.

PURPOSETo determine the effect of proximal flow arrest on the frequency and timing of distal embolic events during occlusion of the common femoral artery with detachable coils.METHODSTwenty-three complex fibered platinum coils were delivered into 10 common femoral arteries without proximal flow arrest. The arteries were continuously monitored for flow and embolic events by Doppler sonography during delivery and for at least 10 minutes after delivery of each coil. Thirty-four coils were delivered into 6 arteries after proximal flow arrest by inflation of a nondetachable balloon. After balloon deflation, each artery was monitored by Doppler sonography for 10 minutes.RESULTSIn the 10 arteries occluded without flow arrest, 87 events (8.7 per artery) occurred, of which 47 were embolic and 40 were indeterminate. In the 6 arteries with flow arrest, the number of emboli detected was 3 (0.5 per artery). Embolic events occurred only if there was residual flow. In those arteries that were occluded when the flow-arrest balloon was deflated, no emboli were detected.CONCLUSIONSProximal flow arrest virtually eliminates the risk of distal emboli during arterial occlusion with detachable fibered coils. The use of fibered coils, in conjunction with proximal flow arrest, allows for safe arterial occlusion when detachable balloons are not available or their use is not feasible.     

Quantitative and qualitative changes in histone gene expression during early mouse embryo development.

There are large amounts of histone mRNA present in mouse eggs. These RNAs are rapidly degraded, as are other mRNAs, after fertilization and prior to the second cleavage. During cleavage, the histone mRNA accumulates as the embryo divides. The same sets of histone genes are expressed in eggs and embryos, although there are large qualitative differences in the amounts of particular histone mRNAs. The function of the egg histone mRNA is unknown. The amount of histone mRNA in cleaving and blastocyst embryos is probably sufficient to code for the blastocyst histone proteins.     

The erythrocyte sedimentation rate in end-stage renal failure

The effect of end-stage renal failure and the dialytic process on erythrocyte sedimentation rate (ESR) is largely unknown. We prospectively studied 60 stable patients with end-stage renal disease to determine the prevalence of elevated ESR in this population. ESRs were also measured immediately pre- and postdialysis in 48 hemodialysis patients. ESR was found to be elevated (greater than or equal to 25 mm/h, Westergren method) in 93% of patients with end-stage renal failure. Fifty-seven percent of patients had marked elevation of ESR (greater than 60 mm/h), while 20% had extreme increases in ESR (greater than or equal to 100 mm/h). In a linear models analysis, aging (P less than .02), anemia (P less than .01), and hypocalcemia (P less than .0001) correlated significantly with ESR elevation. Midweek BUN and creatinine, type and duration of dialysis, cause of renal failure, and serum albumin and total protein measurements did not correlate with ESR. In 48 stable in-center hemodialysis patients, mean predialysis ESR of 70 +/- 4 mm/h was not significantly different from mean postdialysis ESR of 72 +/- 5 mm/h. Retrospective chart review of available ESRs prior to initiation of any dialysis treatment also revealed significant elevation of ESR, mean 82 +/- 9 mm/h, in patients with renal disease not yet on dialysis. An upward trend in ESR during acute illness (74 +/- 9 to 95 +/- 8, N = 10) was observed. In a subpopulation of patients, fibrinogen correlated significantly with ESR while gamma-globulins did not. We conclude that measurement of ESR in end-stage renal failure has little clinical utility. Possible explanations for acceleration of ESR in this population are discussed.