Degradation of bone structural properties by accumulation and coalescence of microcracks

Failure of bone adaptation to protect the skeleton from fatigue fracture is common, and site-specific accumulation and coalescence of microcracking in regions of high strain during cyclic loading is considered a key factor that decreases the resistance of whole bones to fracture. We investigated the effect of cyclic fatigue loading on the monotonic structural properties of the rat ulna during accumulation and coalescence of microcracks. Cyclic end-loading of the ulna was performed at 4 Hz ex vivo at an initial peak strain of -6000 muepsilon to 20% loss of stiffness (n = 7) or 40% loss of stiffness (n = 7) bilaterally. A 0% loss of stiffness monotonically loaded control group (n = 7) was also included. Volumetric bone mineral density (vBMD), ultimate strength (F(u)), stiffness (S), and energy-to-failure (U) were determined in one ulna and in the contralateral ulna vBMD, cortical bone area (B.Ar), maximum and minimum second moments of inertia (I(MAX) and I(MIN)), microcrack density (Cr.Dn), microcrack mean length (Cr.Le), and microcrack surface density (Cr.S.Dn) were determined. In two additional groups of rats, cyclic end-loading of the ulna was also performed ex vivo unilaterally to 20% loss of stiffness (n = 10) and 40% loss of stiffness (n = 10) and then vBMD, F(u), S, U, B.Ar, I(MAX), and I(MIN) were determined bilaterally. Fatigue loading had incremental degradative effects on ulna structural properties. This decreased resistance to fracture was associated with accumulation and coalescence of branching arrays of microcracks within the cortex of the ulna. Microcracking was most prominent in the middiaphysis and corresponded to the region of the bone that fractured during monotonic structural testing. Fatigue loading influenced the relationship between bone cross-sectional geometry and vBMD and ulna structural properties. At 40% loss of stiffness, F(u), S, and U were all significantly correlated with cross-sectional bone geometry and vBMD, whereas this was not the case at 20% loss of stiffness and with the 0% loss of stiffness monotonic control ulnae. We also found a biologically significant individual animal effect. Larger ulnae required a higher number of load cycles for fatigue to develop, retained higher strength, and accumulated a greater amount of microcracking at the end of the cyclic fatigue testing. Small increases in bone size and density can substantially improve the resistance of whole bones to fracture as microcracking accumulates and coalesces during cyclic fatigue loading.     

Severe carpal tunnel syndrome potentially needing surgical treatment in a general population

PURPOSE: To estimate the prevalence of severe carpal tunnel syndrome (CTS) that potentially needs surgical treatment in a general population. METHODS: A health-status questionnaire was mailed to a random general population sample of 3,000 subjects (ages, 25-74 y). The responders who reported numbness and/or tingling in the median nerve distribution in the hands were asked to attend a clinical evaluation at which they completed the validated CTS questionnaire and underwent physical examination and nerve conduction tests. The CTS questionnaire measures the severity of symptoms and disability on a scale from 1 (none) to 5 (most severe). The potential need for surgery was defined as CTS symptom severity score of 3.2 or greater or functional status score of 2.5 or greater (corresponding to median preoperative scores for surgical patients in previous reports). RESULTS: The response rate for the survey was 83%. Of the responders who reported numbness and/or tingling in the median nerve distribution in the hands 81% attended the clinical evaluation. Of the 94 subjects diagnosed with clinically certain CTS, 19 (20%; 12 with electrophysiologically proven median neuropathy) had previously undiagnosed CTS that potentially needed surgical treatment, yielding a population prevalence of 7 per 1,000 (95% confidence interval, 4-11 per 1,000). CONCLUSIONS: In a general population there was a 0.7% prevalence of undiagnosed CTS with a severity similar to that of patients undergoing surgery. The degree to which variable numbers of this group are drawn into a medical system could account for variations in the rate of surgery performed.     

Vascular endothelial growth factor production in human prostate cancer cells is stimulated by overexpression of platelet 12-lipoxygenase

BACKGROUND: Elevated platelet 12-Lipoxygenase (P12-LOX) expression is associated with advanced stage and grade prostate cancer and overexpression in PC-3 cells promotes tumor growth and angiogenesis. The mechanisms underlying the role of P12-LOX in angiogenesis remain unclear. METHODS: Enzyme linked immunosorbent assays were used to measure 12(S)-hydroxyeicosatetraenoic acid (12(S)-HETE) and vascular endothelial growth factor (VEGF) in conditioned media of PC-3 cells stably overexpressing human P12-LOX. Immunoblotting was used to observe stimulation of signal transduction in prostate cancer cell lines following exposure to 12(S)-HETE. RESULTS: P12-LOX overexpression promotes increased accumulation of 12(S)-HETE and VEGF in culture media leading to constitutive ERK1/2 phosphorylation. 12(S)-HETE stimulates ERK1/2 phosphorylation via a pertussis toxin sensitive G-protein coupled receptor (GPCR) and MEK; the inhibition of which reduces VEGF accumulation by 36% and 70%, respectively. CONCLUSIONS: Our data provide insight into a possible mechanism by which prostate cancer cells with elevated expression of P12-LOX stimulate VEGF production, thus increasing their angiogenic potential.     

Serum-free cultures of murine adrenal cortical cells

Purpose

The feasibility of culturing murine adrenal cortical cells before transplantation was investigated in this study.

Method

Primary murine adrenal cortical cells were maintained in either fetal bovine and horse sera-containing media or serum-free media. Real-time polymerase chain reaction was used to quantify the levels of adrenal cortical gene expression in the cultured cells.

Results

The use of sera-containing media led to the growth of many cells in the culture, but the expression of Sf-1, Dax-1, and Cyp11b1 in such cultures declined rapidly. In contrast, there was no significant cell growth in the serum-free culture medium. Culturing murine adrenal cortical cells in the serum-free medium resulted in higher levels of Sf-1, Dax-1, and Cyp11b1 gene expression. In the serum-free medium, adrenal cortical cells also responded to adrenocorticotropic hormone by increasing the expression of Cyp11b1 and suppressing the expression of Dax-1 in a dose-dependent manner. The addition of basic fibroblast growth factor to the serum-free medium maintained the expression of Sf-1, Dax-1, and Cyp11b1 for 4 weeks.

Conclusion

Adrenal cortical cells isolated from adult mice were successfully maintained in a serum-free culture medium with basic fibroblast growth factor. This culture system may be suitable for further manipulation of adrenal cortical cells in vitro before transplantation.     

Plasma verapamil levels and exercise performance

Our study in 10 patients with stable, exercise-related angina under a double-blind, placebo-controlled protocol correlated plasma verapamil levels after single oral doses of 120 and 240 mg and exercise performance. Plasma verapamil levels peaked at 2 hr in seven patients and 4 hr in three patients and declined thereafter, with a mean plasma t1/2 of 3.22 and 4.54 hr after the 120- and 240-mg dose. Despite the relatively short t1/2s, total exercise duration and time to onset of angina and S-T segment depression were longer than placebo values for 4 hr after the 120-mg dose and for 8 hr after the 240-mg dose. Percentage increase in treadmill time and log of plasma verapamil levels correlated. All patients with plasma levels above 100 ng/ml had at least a 50% increase in exercise duration. Thus measurement of plasma verapamil levels are useful in patients who fail to respond to a dose of verapamil. If the level is below 100 ng/ml, increasing the dose of verapamil may improve response.     

Ketoconazole protects against infection with Trypanosoma cruzi in a murine model

The oral administration of ketoconazole to mice protected them against death caused by infection with Trypanosoma cruzi. The addition of ketoconazole to cultures of macrophages infected with the organism markedly inhibited the intracellular multiplication of amastigotes. These observations suggest that ketoconazole may be a potent agent against T. cruzi and should be evaluated more extensively as a chemotherapeutic agent for Chagas' disease.     

Dentine bonding agents--characteristic bond strength as a function of dentine depth.

The tensile bond strength to dentine of four dentine bonding agents has been measured at various depths within dentine and the results analysed using Weibull analysis. There were significant differences in the bond strength values among the four products particularly with near-surface dentine. Despite the differences in chemical composition among the materials the trend of decreasing bond strength with increasing depth of dentine was common to them all. This suggests that the underlying mechanism of adhesion may be common to all four products despite their differing chemical compositions.