Androgens regulate bone resorption activity of isolated osteoclasts in vitro

For many years it has been recognized that sex steroids have profound effects on bone metabolism. The current perception is that estrogen decreases bone resorption and androgen increases bone deposition. To investigate the potential for androgens to directly modulate bone resorption, we have examined avian osteoclast and human and mouse osteoclast-like cells for androgen responsiveness. There was a dose-dependent decrease in resorption activity in response to α-dihydrotestosterone (α-DHT), β-DHT, testosterone, or the synthetic androgen RU1881. This decrease was blocked by cotreatment with the specific androgen antagonist hydroxyflutamide. Further examination of avian osteoclasts revealed that the cells exhibited specific and saturable nuclear binding of tritiated RU1881 and that α-DHT stimulated the activity of the androgen response element as measured by using a chloramphenicol acetyltransferase reporter plasmid. In addition, avian osteoclasts responded to androgen treatment with elevated production and secretion of transforming growth factor β, a well documented response to androgen exposure in other cell systems. Treatment with either α-DHT or β-DHT for 24 hours resulted in a significant dose-dependent decrease in secretion of cathepsin B and tartrate-resistant acid phosphatase. This response to β-DHT, a stereoisomer of α-DHT that is inactive in other androgen receptor-dependent systems, supports the hypothesis that the osteoclast androgen receptor has unusual ligand-binding properties. Taken together, these results confirm the presence of functional androgen receptors in these cells and support the conclusion that osteoclasts are able to respond directly to androgens in vitro and thus are potential androgen target cells in vivo.     

Is Cerebral Microembolism in Mechanical Prosthetic Heart Valves Clinically Relevant?

BACKGROUND AND PURPOSE: High-intensity transient signals (HITS) are frequently detected by transcranial Doppler (TCD) ultrasound in patients with mechanical prosthetic heart valves (PHVs), but published data about their clinical relevance are controversial. This study was undertaken to determine the clinical relevance of HITS in patients with mechanical PHVs. METHODS: The authors prospectively studied patients with mechanical PHVs using TCD monitoring for microemboli detection with and without O2 inhalation. The cognitive testing of patients included the Mini-Mental State Examination, the Dementia Rating Scale, and MicroCog. RESULTS: The authors studied 36 patients (20 women, aged 58 +/- 13 years). HITS were detected in 72% of patients, with a nonsignificant increase of HITS rate in the aortic valve group (P = .07). There was no significant difference in HITS rate between asymptomatic and symptomatic patients. In a multiple linear regression model, HITS rate was predicted only by younger age (P = .024). No correlation was found between HITS rate and the cognitive performance of patients. There was a significant decrease in HITS rate after 100% O2 inhalation compared to baseline levels (32.8 +/- 40.2 vs 6.1 +/- 11.3, P = .011). Subgroup analysis in asymptomatic patients confirmed this finding (P = .017), but in symptomatic patients, decreased HITS rate was not statistically significant (P = .18). CONCLUSION: Only age was a significant predictor of HITS in patients with mechanical PHVs. The lack of association between HITS, clinical symptoms, and cognitive functioning suggests that most of these signals represent harmless epiphenomena, and only HITS detected after O2 inhalation have any clinical relevance.     

Bactericidal Activity and Postantibiotic Effect of Levofloxacin against Anaerobes

The bactericidal activity and postantibiotic effect (PAE) of levofloxacin against nine anaerobes were determined. Levofloxacin at concentrations of the MIC and twice the MIC was bactericidal at 24 h to five of nine and nine of nine strains, respectively. The PAE of levofloxacin following a 2-h exposure ranged from 0.06 to 2.88 h.     

Retinal image quality for virtual eyes generated by a statistical model of ocular wavefront aberrations

A statistical model of the aberration structure of normal, well-corrected eyes was developed previously ( Opthal. Physiol. Opt 22 , 427–433, 2002.) from wavefront aberrations measured for 100 normal eyes ( J. Opt. Soc. Am. A. 19 , 2329–2348, 2002.). The model is capable of generating an unlimited number of wavefront aberration functions for virtual eyes drawn randomly from a multivariate Gaussian distribution of Zernike aberration coefficients. This report provides evidence that monochromatic retinal image quality in virtual eyes, as quantified by 31 different image quality metrics ( J. Vis. 4 , 329–351, 2004.), is representative of human eyes but slightly exaggerates the degradation of the retinal image caused by ocular aberrations. A demonstration program for producing virtual eyes is included as an Appendix to this paper.     

Loss of estrogen receptor β decreases mitochondrial energetic potential and increases thrombogenicity of platelets in aged female mice

Platelets derived from aged (reproductively senescent) female mice with genetic deletion of estrogen receptor beta (βER) are more thrombogenic than those from age-matched wild-type (WT) mice. Intracellular processes contributing to this increased thrombogenicity are not known. Experiments were designed to identify subcellular localization of estrogen receptors and evaluate both glycolytic and mitochondrial energetic processes which might affect platelet activation. Platelets and blood from aged (22–24 months) WT and estrogen receptor β knockout (βERKO) female mice were used in this study. Body, spleen weight, and serum concentrations of follicle-stimulating hormone and 17β-estradiol were comparable between WT and βERKO mice. Number of spontaneous deaths was greater in the βERKO colony (50% compared to 30% in WT) over the course of 24 months. In resting (nonactivated) platelets, estrogen receptors did not appear to colocalize with mitochondria by immunostaining. Lactate production and mitochondrial membrane potential of intact platelets were similar in both groups of mice. However, activities of NADH dehydrogenase, cytochrome bc ₁ complex, and cytochrome c oxidase of the electron transport chain were reduced in mitochondria isolated from platelets from βERKO compared to WT mice. There were a significantly higher number of phosphatidylserine-expressing platelet-derived microvesicles in the plasma and a greater thrombin-generating capacity in βERKO compared to WT mice. These results suggest that deficiencies in βER affect energy metabolism of platelets resulting in greater production of circulating thrombogenic microvesicles and could potentially explain increased predisposition to thromboembolism in some elderly females.     

Lens proteomics: analysis of rat crystallin sequences and two-dimensional electrophoresis map.

PURPOSE: To determine the sequence of four rat beta-crystallins, confirm the sequences by mass spectrometry, and produce a two-dimensional electrophoresis (2-DE) map of soluble crystallins in young rat lens. METHODS: New or additional sequences were determined for betaB1, betaB3, betaA3, and betaA4-crystallin cDNAs from Sprague-Dawley rats, and the deduced protein sequences confirmed by mass spectrometry. The identity and relative abundance of each crystallin was then determined by 2-DE of soluble protein from whole lenses of 12-day-old rats, image analysis, and tandem mass spectrometry (MS/MS) spectra of peptides from in-gel digests. RESULTS: The previously unreported sequence of rat betaA4 cDNA encoded a 195-amino-acid protein. Additional cDNA sequencing provided the previously unknown N-terminal sequence of rat betaA3, found two differences from the previous amino acid sequences of both rat betaB1 and betaB3, and detected a polymorphism at residue 54 in rat betaB3. These new sequences were then confirmed by whole protein masses and MS/MS spectra of proteolytic digests. 2-DE analysis provided a more detailed map of rat crystallins than previously available and allowed the composition of crystallins in young rat lens to be compared with that in young human lens. CONCLUSIONS: This report provides baseline data that will facilitate the analysis of posttranslational modifications in rat crystallins during cataract. Detection of a polymorphism in the sequence of rat betaB3 suggests that crystallins in humans could also exhibit polymorphisms. The unusual abundance of rat betaB3 and low abundance of betaB2 may account for the increased susceptibility of rat crystallins to insolubilization during aging and cataract.     

Effectiveness of pharmacy policies designed to limit inappropriate vancomycin use: a population-based assessment.

OBJECTIVE: In Oregon in 1994, a population-based study of 66 nonpsychiatric hospitals indicated that 40% of vancomycin orders were inappropriate according to Centers for Disease Control and Prevention guidelines. We repeated the study to determine whether vancomycin use had been affected by pharmacy policies implemented following the 1994 study. METHODS: We surveyed pharmacists in nonpsychiatric hospitals in Oregon regarding vancomycin use policies in their hospitals. Using pharmacy records, we identified and abstracted the charts of all patients in Oregon hospitals receiving vancomycin during a 3-week period to determine appropriate use of vancomycin. RESULTS: Thirteen (20%) of 64 hospitals had implemented a vancomycin restriction policy since 1994; none ofthe remaining hospitals in the study had a policy. In 1999, hospitals with vancomycin restriction policies had substantially decreased rates of inappropriate vancomycin use compared with hospitals without such policies (1.0 vs 1.8 orders per 1,000 patient-days; P = .01). Compared with 1994 baseline rates of inappropriate use, hospitals that adopted policies experienced a decrease (from 1.5 orders per 1,000 patient-days in 1994 to 1.0 in 1999; P= .13), whereas hospitals without policies experienced a statistically significant increase (from 0.9 orders per 1,000 patient-days in 1994 to 1.8 in 1999; P= .001). Restriction policies were most effective at reducing rates of inappropriate use for treatment of confirmed gram-positive infections and prophylaxis. CONCLUSION: Vancomycin restriction policies were associated with a decrease in inappropriate therapeutic and prophylactic vancomycin use, but had no effect on inappropriate empiric use. Hospitals considering limits regarding inappropriate use should consider implementation of institution-based vancomycin restriction policies as part of an overall strategy.