Reference values and clinical predictors of bone strength for HR-pQCT-based distal radius and tibia strength assessments in women and men.

Reference values for radius and tibia strength using multiple-stack high-resolution peripheral quantitative computed tomography (HR-pQCT) with homogenized finite element analysis are presented in order to derive critical values improving risk prediction models of osteoporosis. Gender and femoral neck areal bone mineral density (aBMD) were independent predictors of bone strength. INTRODUCTION: The purpose was to obtain reference values for radius and tibia bone strength computed by using the homogenized finite element analysis (hFE) using multiple stacks with a HR-pQCT. METHODS: Male and female healthy participants aged 20-39 years were recruited at the University Hospital of Bern. They underwent interview and clinical examination including hand grip, gait speed and DXA of the hip. The nondominant forearm and tibia were scanned with a double and a triple-stack protocol, respectively, using HR-pQCT (XCT II, SCANCO Medical AG). Bone strength was estimated by using the hFE analysis, and reference values were calculated using quantile regression. Multivariable analyses were performed to identify clinical predictors of bone strength. RESULTS: Overall, 46 women and 41 men were recruited with mean ages of 25.1 (sd 5.0) and 26.2 (sd 5.2) years. Sex-specific reference values for bone strength were established. Men had significantly higher strength for radius (mean (sd) 6640 (1800) N vs. 4110 (1200) N; p < 0.001) and tibia (18,200 (4220) N vs. 11,970 (3150) N; p < 0.001) than women. In the two multivariable regression models with and without total hip aBMD, the addition of neck hip aBMD significantly improved the model (p < 0.001). No clinical predictors of bone strength other than gender and aBMD were identified. CONCLUSION: Reference values for radius and tibia strength using multiple HR-pQCT stacks with hFE analysis are presented and provide the basis to help refining accurate risk prediction models. Femoral neck aBMD and gender were significant predictors of bone strength.

Chronic γ-secretase inhibition reduces amyloid plaque-associated instability of pre- and postsynaptic structures.

The loss of synapses is a strong histological correlate of the cognitive decline in Alzheimer's disease (AD). Amyloid ß-peptide (Aß), a cleavage product of the amyloid precursor protein (APP), exerts detrimental effects on synapses, a process thought to be causally related to the cognitive deficits in AD. Here, we used in vivo two-photon microscopy to characterize the dynamics of axonal boutons and dendritic spines in APP/Presenilin 1 (APP(swe)/PS1(L166P))-green fluorescent protein (GFP) transgenic mice. Time-lapse imaging over 4 weeks revealed a pronounced, concerted instability of pre- and postsynaptic structures within the vicinity of amyloid plaques. Treatment with a novel sulfonamide-type γ-secretase inhibitor (GSI) attenuated the formation and growth of new plaques and, most importantly, led to a normalization of the enhanced dynamics of synaptic structures close to plaques. GSI treatment did neither affect spines and boutons distant from plaques in amyloid precursor protein/presenilin 1-GFP (APPPS1-GFP) nor those in GFP-control mice, suggesting no obvious neuropathological side effects of the drug.

A phase 2 multiple ascending dose trial of bapineuzumab in mild to moderate Alzheimer disease.

BACKGROUND: Bapineuzumab, a humanized anti-amyloid-beta (Abeta) monoclonal antibody for the potential treatment of Alzheimer disease (AD), was evaluated in a multiple ascending dose, safety, and efficacy study in mild to moderate AD. METHODS: The study enrolled 234 patients, randomly assigned to IV bapineuzumab or placebo in 4 dose cohorts (0.15, 0.5, 1.0, or 2.0 mg/kg). Patients received 6 infusions, 13 weeks apart, with final assessments at week 78. The prespecified primary efficacy analysis in the modified intent-to-treat population assumed linear decline and compared treatment differences within dose cohorts on the Alzheimer's Disease Assessment Scale-Cognitive and Disability Assessment for Dementia. Exploratory analyses combined dose cohorts and did not assume a specific pattern of decline. RESULTS: No significant differences were found in the primary efficacy analysis. Exploratory analyses showed potential treatment differences (p < 0.05, unadjusted for multiple comparisons) on cognitive and functional endpoints in study "completers" and APOE epsilon4 noncarriers. Reversible vasogenic edema, detected on brain MRI in 12/124 (9.7%) bapineuzumab-treated patients, was more frequent in higher dose groups and APOE epsilon4 carriers. Six vasogenic edema patients were asymptomatic; 6 experienced transient symptoms. CONCLUSIONS: Primary efficacy outcomes in this phase 2 trial were not significant. Potential treatment differences in the exploratory analyses support further investigation of bapineuzumab in phase 3 with special attention to APOE epsilon4 carrier status. CLASSIFICATION OF EVIDENCE: Due to varying doses and a lack of statistical precision, this Class II ascending dose trial provides insufficient evidence to support or refute a benefit of bapineuzumab.

Follow up after middle-ear ventilation tube insertion: what is needed and when?

INTRODUCTION: There is a paucity of evidence to guide the post-operative follow up of patients undergoing middle-ear ventilation tube insertion for the first time. This study was conceived to identify current practice at our institution (Ninewells Hospital, Dundee) and to inform subsequent change in our follow-up procedure. METHODS: Two cycles of data collection and analysis were performed. All paediatric patients undergoing ventilation tube insertion for the first time were identified. Patients who had previously undergone ventilation tube insertion or additional procedures such as adenoidectomy or tonsillectomy were excluded. The first data collection period comprised all of the year 2000, and the second 18 months over 2003-2004. A minimum of 20 months' follow up was allowed for. Data regarding clinical findings and audiometry were recorded at each follow-up appointment. RESULTS: We identified a total of 50 patients meeting our criteria for inclusion in the first cohort. There were a total of 156 appointments between surgery and data collection (a mean of 3.12 per child). A total of 113 (72 per cent) appointments lead to no medical intervention. The only statistically significant difference between patients requiring further ventilation tube insertion (n = 10) and those not requiring further treatment during the study period (n = 40) was the average hearing threshold (p < 0.01). These findings prompted a change in the post-operative regime; all patients undergoing ventilation tube insertion were subsequently seen at three months for a pure tone audiogram, and further review depended on clinical and audiometric findings. Records for 84 children were identified and collected for the second cohort, there were a total of 154 appointments (a mean of 1.83 per child). In only 18 appointments (12 per cent) were normal findings and hearing recorded and children given a further review appointment. Sixteen of 29 (55 per cent) children with abnormal clinical findings (otorrhoea, tube blockage or extrusion) required some form of intervention (p < 0.05). Twenty-six had a mean hearing threshold worse than 20 dB at first review. Nineteen (73 per cent) required further intervention of some sort (p < 0.01). CONCLUSIONS: Our study demonstrated that the vast majority of review appointments resulted in no clinical intervention. We therefore question the need for regular follow up in this patient group. Twenty per cent (10 of 50 and 18 of 84) of our patients required further ventilation tube insertion within the study periods. This is consistent with rates reported in the literature. Children with abnormal clinical findings or a mean hearing threshold greater than 20 dB were significantly more likely to require further intervention. We would recommend one post-operative review with audiometry, three months after surgery. At this initial appointment, further review should be offered to those children with poor hearing, early extrusion, blockage or infection, as they are more likely to require further ventilation tube insertion. This strategy is dependent on good links with community primary care providers and easy access to secondary care for further management, should this be required.

Inter- and intralaboratory variation of in vitro diffusion cell measurements: an international multicenter study using quasi-standardized methods and materials.

In vitro measurements of skin absorption are an increasingly important aspect of regulatory studies, product support claims, and formulation screening. However, such measurements are significantly affected by skin variability. The purpose of this study was to determine inter- and intralaboratory variation in diffusion cell measurements caused by factors other than skin. This was attained through the use of an artificial (silicone rubber) rate-limiting membrane and the provision of materials including a standard penetrant, methyl paraben (MP), and a minimally prescriptive protocol to each of the 18 participating laboratories. "Standardized" calculations of MP flux were determined from the data submitted by each laboratory by applying a predefined mathematical model. This was deemed necessary to eliminate any interlaboratory variation caused by different methods of flux calculations. Average fluxes of MP calculated and reported by each laboratory (60 +/- 27 microg cm(-2) h(-1), n = 25, range 27-101) were in agreement with the standardized calculations of MP flux (60 +/- 21 microg cm(-2) h(-1), range 19-120). The coefficient of variation between laboratories was approximately 35% and was manifest as a fourfold difference between the lowest and highest average flux values and a sixfold difference between the lowest and highest individual flux values. Intralaboratory variation was lower, averaging 10% for five individuals using the same equipment within a single laboratory. Further studies should be performed to clarify the exact components responsible for nonskin-related variability in diffusion cell measurements. It is clear that further developments of in vitro methodologies for measuring skin absorption are required.

Abeta vaccination effects on plaque pathology in the absence of encephalitis in Alzheimer disease.

The authors report a patient with Alzheimer disease (AD) without encephalitis who was immunized with AN-1792 (an adjuvanted formulation of Abeta-42). There were no amyloid plaques in the frontal cortex and abundant Abeta-immunoreactive macrophages, but tangles and amyloid angiopathy were present. The white matter appeared normal and minimal lymphocytic infiltration in the leptomeninges was observed. This case illustrates the effects of an Abeta-based immunization on AD pathogenesis in the absence of overt meningoencephalitis and leukoencephalopathy.

Postpericardiotomy syndrome after minimally invasive pectus excavatum repair unresponsive to nonsteroidal anti-inflammatory treatment.

A 14-year-old boy developed postpericardiotomy syndrome after an otherwise uneventful minimally invasive pectus excavatum repair. Dyspnoea, chest pain, and pericardial effusion progressed despite nonsteroidal anti-inflammatory treatment. The symptoms rapidly resolved with intravenous methylprednisolone, and pericardiocentesis was thus avoided. This is the first report of postpericardiotomy syndrome after the Nuss procedure treated with systemic steroids.

Cloning, heterologous expression, and functional characterization of 5-epi-aristolochene-1,3-dihydroxylase from tobacco (Nicotiana tabacum).

Capsidiol is a bicyclic, dihydroxylated sesquiterpene produced by several solanaceous species in response to a variety of environmental stimuli. It is the primary antimicrobial compound produced by Nicotiana tabacum in response to fungal elicitation, and it is formed via the isoprenoid pathway from 5-epi-aristolochene. Much of the biosynthetic pathway for the formation of this compound has been elucidated, except for the enzyme(s) responsible for the conversion of 5-epi-aristolochene to its dihydroxylated form, capsidiol. Biochemical evidence from previous studies with N. tabacum (Whitehead, I. M., Threlfall, D. R., and Ewing, D. F., 1989, Phytochemistry 28, 775-779) and Capsicum annuum Hoshino, T., Yamaura, T., Imaishi, H., Chida, M., Yoshizawa, Y., Higashi, K., Ohkawa, H., Mizutani, J., 1995, Phytochemistry 38, 609-613. suggested that the oxidation of 5-epi-aristolochene to capsidiol was mediated by at least one elicitor-inducible cytochrome P450 hydroxylase. In extending these observations, we developed an in vivo assay for 5-epi-aristolochene hydroxylase activity and used it to demonstrate a dose-dependent inhibition of activity by ancymidol and ketoconazole, two well characterized inhibitors of cytochrome P450 enzymes. Using degenerate oligonucleotide primers designed to the well conserved domains found within most P450 enzymes, including the heme binding domain, cDNA fragments representing four distinct P450 families (CYP71, CYP73, CYP82, and CYP92) were amplified from a cDNA library prepared against mRNA from elicitor-treated cells using PCR. The PCR fragments were subsequently used to isolate full-length cDNAs (CYP71D20 and D21, CYP73A27 and A28, CYP82E1 and CYP92A5), and these in turn were used to demonstrate that the corresponding mRNAs were all induced in elicitor-treated cells, albeit with different induction patterns. Representative, full-length cDNAs for each of the P450s were engineered into a yeast expression system, and the recombinant yeast assessed for functional expression of P450 protein by measuring the CO difference spectra of the yeast microsomes. Only microsomal preparations from yeast expressing the CYP71D20 and CYP92A5 cDNAs exhibited significant CO difference absorbance spectra at 450 nm and were thus tested for their ability to hydroxylate 5-epi-aristolochene and 1-deoxycapsidiol, a putative mono-hydroxylated intermediate in capsidiol biosynthesis. Interestingly, the CYP71D20-encoded enzyme activity was capable of converting both 5-epi-aristolochene and 1-deoxycapsidiol to capsidiol in vitro, consistent with the notion that this P450 enzyme catalyzes both hydroxylations of its hydrocarbon substrate.

Encapsulation in biodegradable microparticles enhances serum antibody response to parenterally-delivered beta-amyloid in mice.

Poly(lactide-co-glycolide) (PLG) microspheres were tested as a parenteral delivery system for human beta-amyloid (1-42) (Abeta), a potential immunotherapeutic undergoing assessment in Phase 1 studies for Alzheimer's disease (AD). Abeta was successfully encapsulated in PLG microspheres of average sizes of 3 or 15 microm diameter. Swiss Webster (SW) mice were injected by the sub-cutaneous (s.c.) or intra-peritoneal (i.p.) routes with 3-33 microg Abeta. Abeta-PLG microparticles (3 microm) induced dose-dependent antibody responses, which were maximal at 33 microg Abeta, while Abeta in phosphate-buffered saline (PBS) produced weak antibody responses at the same doses by both routes. Significantly increased antibody responses were seen for both small and large particle formulations given by the i.p. route in comparison to the s.c route. It was previously reported that passive immunisation with Abeta-specific antibodies cleared amyloid plaques in a mouse model of AD (Bard F, Cannon C, Barbour R, et al. Peripherally administered antibodies against amyloid beta-peptide enter the nervous system and reduce pathology in a mouse model of Alzheimer disease. Nature Med 2000;6:916-19), an indication that induction of serum antibody is a prerequisite for efficacy.

BACE knockout mice are healthy despite lacking the primary beta-secretase activity in brain: implications for Alzheimer's disease therapeutics.

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by accumulation of amyloid plaques and neurofibrillary tangles in the brain. The major components of plaque, beta-amyloid peptides (Abetas), are produced from amyloid precursor protein (APP) by the activity of beta- and gamma-secretases. beta-secretase activity cleaves APP to define the N-terminus of the Abeta1-x peptides and, therefore, has been a long- sought therapeutic target for treatment of AD. The gene encoding a beta-secretase for beta-site APP cleaving enzyme (BACE) was identified recently. However, it was not known whether BACE was the primary beta-secretase in mammalian brain nor whether inhibition of beta-secretase might have effects in mammals that would preclude its utility as a therapeutic target. In the work described herein, we generated two lines of BACE knockout mice and characterized them for pathology, beta-secretase activity and Abeta production. These mice appeared to develop normally and showed no consistent phenotypic differences from their wild-type littermates, including overall normal tissue morphology and brain histochemistry, normal blood and urine chemistries, normal blood-cell composition, and no overt behavioral and neuromuscular effects. Brain and primary cortical cultures from BACE knockout mice showed no detectable beta-secretase activity, and primary cortical cultures from BACE knockout mice produced much less Abeta from APP. The findings that BACE is the primary beta-secretase activity in brain and that loss of beta-secretase activity produces no profound phenotypic defects with a concomitant reduction in beta-amyloid peptide clearly indicate that BACE is an excellent therapeutic target for treatment of AD.

Accumulation of amyloid beta-protein in the low-density membrane domain accurately reflects the extent of beta-amyloid deposition in the brain.

To learn more about the process of amyloid beta-protein (Abeta) deposition in the brain, human prefrontal cortices were fractionated by sucrose density gradient centrifugation, and the Abeta content in each fraction was quantified by a two-site enzyme-linked immunosorbent assay. The fractionation protocol revealed two pools of insoluble Abeta. One corresponded to a low-density membrane domain; the other was primarily composed of extracellular Abeta deposits in those cases in which Abeta accumulated to significant levels. Abeta42 levels in the low-density membrane domain were proportional to the extent of total Abeta42 accumulation, which is known to correlate well with overall amyloid burden. In PDAPP mice that form senile plaques and accumulate Abeta in a similar manner to aging humans, Abeta42 accumulation in the low-density membrane domain also increased as Abeta deposition progressed with aging. These observations indicate that the Abeta42 associated with low-density membrane domains is tightly coupled with the process of extracellular Abeta deposition.

Functional gamma-secretase inhibitors reduce beta-amyloid peptide levels in brain.

Converging lines of evidence implicate the beta-amyloid peptide (Ass) as causative in Alzheimer's disease. We describe a novel class of compounds that reduce A beta production by functionally inhibiting gamma-secretase, the activity responsible for the carboxy-terminal cleavage required for A beta production. These molecules are active in both 293 HEK cells and neuronal cultures, and exert their effect upon A beta production without affecting protein secretion, most notably in the secreted forms of the amyloid precursor protein (APP). Oral administration of one of these compounds, N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester, to mice transgenic for human APP(V717F) reduces brain levels of Ass in a dose-dependent manner within 3 h. These studies represent the first demonstration of a reduction of brain A beta in vivo. Development of such novel functional gamma-secretase inhibitors will enable a clinical examination of the A beta hypothesis that Ass peptide drives the neuropathology observed in Alzheimer's disease.

Potential treatment opportunities for Alzheimer's disease through inhibition of secretases and Abeta immunization.

Research over the past ten years on Alzheimer's disease has pursued many opportunities. Notable amongst the various approaches are efforts related to the "amyloid hypothesis." This hypothesis posits that the beta amyloid peptide causes the extensive neuropathology and clinical decline associated with the disease. Extensive research in this area has shown that the beta amyloid peptide is produced by proteases termed "secretases" and it has been shown that blockade of secretase functions reduce the amount of beta amyloid peptide produced. An additional approach to reduce beta amyloid, through an increase in clearance mechanisms, is to immunize with the peptide itself and induce an antibody response. The specifically elicited antibodies then bind to and stimulate clearance of the peptide from the brain. These findings have stimulated several approaches to develop novel therapeutic strategies to treat Alzheimer's disease that either are about or have entered the clinic.

Immunotherapy with beta-amyloid for Alzheimer's disease: a new frontier.

Alzheimer's disease (AD) represents the fourth leading cause of death in the U.S. and the leading cause of dementia in the elderly population. Until recently, there was little hope of finding a way to prevent the underlying brain pathology from progressing toward the inevitable conclusion of the disease. However, new immunotherapeutic approaches have been described that are based on vaccination with the beta-amyloid 1-42 peptide (Abeta). The encouraging efficacy and safety of Abeta immunization in reducing neuropathology in animal models of AD has opened up new therapeutic possibilities for patients. Immunization with Abeta is aimed at reducing the Abeta-associated pathology of AD. It is hypothesized that this approach will also reduce the cascade of downstream events leading to neuronal cell loss and, ultimately, dementia. The ensuing articles in this issue describe various aspects of the Abeta immunization strategy and their potential relevance to AD treatment.

Effect of the dietary brominated phenol, lanasol, on chemical biotransformation enzymes in the gumboot chiton Cryptochiton stelleri (Middendorf, 1846).

The effects of diet and other non-anthropogenic stressors on biochemical defenses and their relationship to susceptibility have been largely ignored in wildlife populations. Lanosol is a compound found in relatively high amounts in various marine species of Rhodophyta, including Odonthalia dentata. While previous studies demonstrated that lanosol is a feeding deterrent to several marine herbivores, Cryptochiton stelleri readily feeds upon O. dentata. To examine the effects of lanosol on the profile of biochemical defenses in C. stelleri, chitons were gavaged daily with 0, 1, 2.5, 5, or 10 mg/kg of lanosol. After three days of exposure, digestive gland microsomes were probed for expression of homologous isoforms of cytochromes P450 (CYP1A, CYP3A, and CYP2) and phase II enzymatic activities. Expression of a 43 kDa CYP3A-like protein was increased by approximately 45%, over control following 2.5, 5, and 10 mg/kg treatments. Estradiol hydroxylase activity tended to increase with the dose of lanosol. UDP-glucuronosyl transferase activity was highly variable but appeared to increase at the two highest treatments, while sulfotranserase activity was significantly decreased at the three highest doses. Kinetic studies of GST activity showed lanosol is a non-competitive inhibitor of both CDNB and GSH in the GST-mediated conjugation reaction. These results show that dietary exposure to the brominated-phenol, lanosol, may alter expression and activity of some phase I and II biotransformation enzymes in chitons, potentially providing a dietary advantage for the species.

Peripherally administered antibodies against amyloid beta-peptide enter the central nervous system and reduce pathology in a mouse model of Alzheimer disease.

One hallmark of Alzheimer disease is the accumulation of amyloid beta-peptide in the brain and its deposition as plaques. Mice transgenic for an amyloid beta precursor protein (APP) mini-gene driven by a platelet-derived (PD) growth factor promoter (PDAPP mice), which overexpress one of the disease-linked mutant forms of the human amyloid precursor protein, show many of the pathological features of Alzheimer disease, including extensive deposition of extracellular amyloid plaques, astrocytosis and neuritic dystrophy. Active immunization of PDAPP mice with human amyloid beta-peptide reduces plaque burden and its associated pathologies. Several hypotheses have been proposed regarding the mechanism of this response. Here we report that peripheral administration of antibodies against amyloid beta-peptide, was sufficient to reduce amyloid burden. Despite their relatively modest serum levels, the passively administered antibodies were able to enter the central nervous system, decorate plaques and induce clearance of preexisting amyloid. When examined in an ex vivo assay with sections of PDAPP or Alzheimer disease brain tissue, antibodies against amyloid beta-peptide triggered microglial cells to clear plaques through Fc receptor-mediated phagocytosis and subsequent peptide degradation. These results indicate that antibodies can cross the blood-brain barrier to act directly in the central nervous system and should be considered as a therapeutic approach for the treatment of Alzheimer disease and other neurological disorders.