In vitro osteoclast resorption of bone substitute biomaterials used for implant site augmentation: a pilot study

PURPOSE: This observational study examined the resorptive behavior of normal neonatal rabbit osteoclasts grown on slices of bovine cortical bone as compared to samples of commercially available bone substitute biomaterials. It also examined the surface characteristics of these materials. MATERIALS AND METHODS: The 11 materials tested fell into 3 groups: (1) bone-derived, including freeze-dried human rib block, human demineralized freeze-dried bone, and deproteinated bovine bone; (2) synthetic hydroxyapatites (HA); and (3) synthetic non-HA, including coated methacrylates and coated silica glass. After 4 days in culture, 1 group of samples of each material underwent scanning electron microscopy (SEM) to evaluate resorptive pitting versus controls, while another group underwent tartrate-resistant acid phosphatase staining and light microscopy to examine osteoclast numbers and morphology. The 2 bovine-derived HA materials also underwent immunohistochemical staining and surface chemistry analysis. RESULTS: While most of these materials supported osteoclast attachment, some spreading, and survival in culture, only the bone-derived materials, with the exception of sintered deproteinated bovine bone, showed large scalloped-edged resorption pits with trails and exposed collagen when examined by SEM, although not to the same extent as unprocessed natural bone material. The HA materials and the sintered deproteinated bovine bone showed evidence of etching with smaller pits but no evidence of resorptive trail formation. The non-HA materials showed no evidence of pit formation or trails. Under immunohistochemical staining, Bio-Oss appeared to be positive for type I collagen after osteoclast activity on its surface, while Osteograf/N showed no positive staining. Surface chemistry analysis revealed nitrogen present in Bio-Oss specimens (0.17% to 0.47%), while there was no nitrogen detected in the Osteograf/N (0.00%); the percent nitrogen observed in normal bovine bone controls was 6.01% to 9.25%. DISCUSSION: The bone-derived materials supported osteoclast activity on the material surface in a way that facilitated formation of the more complex resorption pits in vitro. Assuming the rate of pit formation observed in vitro mimics that observed in vivo, the quantity and type of osteoclastic remodeling seen on non-bone-derived materials--and perhaps sintered bone-derived materials--would be extremely slow to negligible. Physiologic removal of non-bone-derived bone substitutes in vivo may occur by methods other than osteoclast resorption. CONCLUSIONS: Allogenous and xenogenous bone-derived materials that undergo delayed physiologic resorption may be more appropriately used with a staged surgical approach when used in sites intended to support osseointegrated dental implants. The combination of collagen staining and the presence of nitrogen suggest that there may be residual protein in Bio-Oss.     

Abnormal cortisol metabolism and tissue sensitivity to cortisol in patients with glucose intolerance

Recent evidence suggests that increased cortisol secretion, altered cortisol metabolism, and/or increased tissue sensitivity to cortisol may link insulin resistance, hypertension, and obesity. Whether these changes are important in type 2 diabetes mellitus (DM) is unknown. We performed an integrated assessment of glucocorticoid secretion, metabolism, and action in 25 unmedicated lean male patients with hyperglycemia (20 with type 2 diabetes and 5 with impaired glucose intolerance by World Health Organization criteria) and 25 healthy men, carefully matched for body mass index, age, and blood pressure. Data are mean +/- SE. Patients with hyperglycemia (DM) had higher HbA(1c) (6.9 +/- 0.2% vs. 6.0 +/- 0.1%, P < 0.0001) and triglycerides. Cortisol secretion was not different, as judged by 0900 h plasma cortisol and 24 h total urinary cortisol metabolites. However, the proportion of cortisol excreted as 5alpha- and 5beta-reduced metabolites was increased in DM patients. Following an oral dose of cortisone 25 mg, generation of plasma cortisol by hepatic 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD 1) was impaired in DM patients (area under the curve, 3617 +/- 281 nM.2 h vs. 4475 +/- 228; P < 0.005). In contrast, in sc gluteal fat biopsies from 17 subjects (5 DM and 12 controls) in vitro 11beta-HSD 1 activity was not different (area under the curve, 128 +/- 56% conversion.30 h DM vs. 119 +/- 21, P = 0.86). Sensitivity to glucocorticoids was increased in DM patients both centrally (0900 h plasma cortisol after overnight 250 micro g oral dexamethasone 172 +/- 16 nM vs. 238 +/- 20 nM, P < 0.01) and peripherally (more intense forearm dermal blanching following overnight topical beclomethasone; 0.56 +/- 0.92 ratio to vehicle vs. 0.82 +/- 0.69, P < 0.05). In summary, in patients with glucose intolerance, cortisol secretion, although normal, is inappropriately high given enhanced central and peripheral sensitivity to glucocorticoids. Normal 11beta-HSD 1 activity in adipose tissue with impaired hepatic conversion of cortisone to cortisol suggests that tissue-specific changes in 11beta-HSD 1 activity in hyperglycemia differ from those in primary obesity but may still be susceptible to pharmacological inhibition of the enzyme to reduce intracellular cortisol concentrations. Thus, altered cortisol action occurs not only in obesity and hypertension but also in glucose intolerance, and could therefore contribute to the link between these multiple cardiovascular risk factors.     

Psychopathology and sexual trauma in childhood and adulthood

This study evaluates the occurrence of psychopathology among 97 women who (1) experienced sexual abuse in childhood only, (2) were raped in adulthood only, (3) experienced both childhood sexual abuse and rape in adulthood, or (4) experienced no sexual trauma. Women were recruited from advertisements and assessed using the Structured Clinical Interview for DSM-IV (SCID-I/P) and the Modified PTSD Symptom Scale Self-Report. Women who reported sexual trauma were significantly more likely to exhibit psychopathology than controls. Being sexually victimized in childhood and raped in adulthood was associated with a particular risk for substance dependence.     

Preoperative detection of pancreatic insulinomas on multiphasic helical CT

OBJECTIVE: The objective was to analyze enhancement characteristics of insulinomas and to determine the ability of multiphase CT to localize these tumors. MATERIALS AND METHODS: Prospective interpretations of multiphase helical CT scans were reviewed in 30 patients who had insulinomas resected over a 5-year period. CT scans were retrospectively reviewed to determine enhancement characteristics, tumor conspicuity in each phase of enhancement, and potential causes for false-negative findings. RESULTS: Sixty-three percent (19/30) of tumors were identified on CT prospectively. An additional six tumors were visualized in retrospect, allowing characterization of 25 (83%) of 30 tumors. Most tumors were hyperdense on at least one phase (n = 19), three tumors were hypoattenuating, and three were isodense and pedunculated. Insulinomas were most conspicuous on the early phase in 15 patients and in the portal venous phase in three. All tumors that underwent pancreatic phase imaging were seen (13/13), whereas three of 18 arterial and six of 25 portal venous phase findings were inconclusive for tumor. In the six examinations with false-negative findings in which the tumor could be seen in retrospect, two tumors were isodense and pedunculated, three were in close proximity to vessels, and one had a cystic appearance. CONCLUSION: Multiphasic CT has a moderate sensitivity in the detection of insulinomas. Most tumors are more conspicuous on the earlier phases of enhancement. The pancreatic phase may be more useful than the arterial phase. Potential sources of false-negative results include tumors adjacent to vessels, pedunculated morphology, or nonhyperattenuating lesions.     

Evaluation activities to strengthen an injury prevention resource center for urban families

The Johns Hopkins Children's Safety Center (CSC) is a unique health care provider and patient education resource that elevates the attention injury prevention receives in a medical setting and reduces barriers to injury prevention experienced by low-income, urban families, the Center's priority population. This article describes the CSC's development, implementation, and selected elements of its evaluation. Because evaluation has played an important role in the CSC from its inception through its implementation and sustainability, three evaluation activities are described: process evaluation to monitor activity, impact evaluation to understand its effects on parents' safety behaviors, and qualitative interviews with CSC visitors and non-visitors to enhance services. Implications of each evaluation activity are described and recommendations are made for strengthening the CSC.     

CYP3A induction by N-hydroxyformamide tumor necrosis factor-alpha converting enzyme/matrix metalloproteinase inhibitors use of a pregname X receptor activation assay and primary hepatocyte culture for assessing induction potential in humans.

A series of N-hydroxyformamide tumor necrosis factor-alpha converting enzyme (TACE)/matrix metalloprotease (MMP) inhibitors were evaluated for their potential to induce human cytochrome P450 3A (CYP3A). Two in vitro assays were used: 1) a cell-based reporter gene assay for activation of the pregnane X receptor (PXR), and 2) a primary "sandwich" culture of human hepatocytes. Approximately 50 TACE/MMP inhibitors were evaluated in the human PXR assay. A range of PXR activation was observed, 0 to 150% of the activation of the known human CYP3A inducer rifampicin. Three TACE/MMP inhibitors were evaluated in rat and human hepatocytes. Significantly higher PXR activation/CYP3A induction was observed in PXR/hepatocyte models, respectively, for (2R,3S) 3-(formyl-hydroxyamino)-2-(2-methyl-1-propyl)-4-methylpentanoic acid [(1S,2S)-2-methyl-1-(2-pyridylcarbamoyl)-1-butyl]amide (GW3333) compared with (2R,3S)-6,6,6-trifluoro-3-[formyl(hydroxy)amino]-2-isobutyl-N-[(1S,2R)-2-methoxy-1-[(1,3-thiazol-2-ylamino)carbonyl]propyl]hexanamide (GW6495) and (2R)-N-[(1S)-2,2-dimethyl-1-[(methylamino)carbonyl]-propyl]-2-[(1S)-1-[formyl(hydroxy)amino]ethyl]-5-phenylpentanamide (GI4023). The CYP3A induction level achieved with GW3333 at a concentration of approximately 10 microM in human hepatocytes was comparable to that achieved with rifampicin at a concentration of 10 microM. The extent of rodent CYP3A induction caused by GW3333 was confirmed in vivo after daily oral administration for 14 days to rats. In conclusion, GW3333 is a potential inducer of CYP3A expression in vivo in humans, but other N-hydroxyformamides are less likely to induce CYP3A.     

Drug interaction potential of soy extract and Panax ginseng

To determine if soy extract or Panax ginseng increases the urinary excretion of the 6-beta-hydroxycortisol/cortisol ratio as a marker of cytochrome P450 (CYP) 3A enzyme induction, subjects received a soy extract containing 50 mg isoflavones twice daily (n = 20) or Panax ginseng 100 mg standardized to 4% ginsenosides twice daily (n = 20) for 14 days. Neither Panax ginseng nor soy extract significantly altered the urinary 6-beta-OH-cortisol/cortisol ratio, suggesting that unlike St. John's wort, they are not CYP3A inducers. Studies in vitro using human liver microsomes were performed to determine the effect of soy extract on probe substrates of CYP and UDP glucuronosyltransferase (UGT). Unhydrolyzed soy extract produced very little inhibition of CYP1A2, CYP2A6, and CYP2D6 and a trend of activation of CYP3A4. Hydrolyzed soy extract showed inhibition of all of the CYPs tested, particularly CYP2C9 and CYP3A4. UGT2B15 was the only UGT significantly inhibited. Even though both soy extract and ginseng have been shown to activate CYP3A4 in vitro, there is a lack of an in vitro correlation with the in vivo effects.