Biomedical subjects
Publications and source records attributed to M J Savage.
We present results of the first fully dynamical lattice QCD determination of nucleon-nucleon scattering lengths in the 1S0 channel and 3S1 - 3D1 coupled channels. The calculations are performed with domain-wall valence quarks on the MILC staggered configurations with a lattice spacing of b = 0.125 fm in the isospin-symmetric limit, and in the absence of electromagnetic interactions.
UNLABELLED: In an observational study of 1335 boys and girls aged 12 and 15 years, higher intakes of carbonated soft drinks (CSDs) were significantly associated with lower bone mineral density at the heel, but only in girls. Owing to the upward trend in CSD intake in adolescence, this finding may be of concern. INTRODUCTION: High consumption of carbonated soft drinks (CSD) during adolescence may reduce bone mineral accrual and increase fracture risk. The aim of this study was to examine the relationship between CSD consumption and bone mineral density (BMD) in a representative sample of adolescents. MATERIALS AND METHODS: This was a cross-sectional observational study in 36 postprimary schools in Northern Ireland. Participants included 591 boys and 744 girls either 12 or 15 years old. BMD was measured by DXA, and usual beverage consumption was assessed by the diet history method. Adjusted regression modeling was used to investigate the influence of CSD on BMD. RESULTS: A significant inverse relationship between total CSD intake and BMD was observed in girls at the dominant heel (beta, -0.099; 95% CI, -0.173 to -0.025). Non-cola consumption was inversely associated with dominant heel BMD in girls (beta, -0.121; 95% CI, -0.194 to -0.048), and diet drinks were also inversely associated with heel BMD in girls (beta, -0.087; 95% CI, -0.158 to -0.016). However, no consistent relationships were observed between CSD intake and BMD in boys. Cola consumption and nondiet drinks were not significantly related to BMD in either sex. CONCLUSION: CSD consumption seems to be inversely related to BMD at the dominant heel in girls. It is possible that the apparent association results from the displacement of more nutritious beverages from the diet. Although the inverse association observed between CSD consumption and BMD is modest and confined to girls, this finding may have important public health implications given the widespread use and current upward trend in CSD consumption in Western populations.
CEP-1347 (KT7515) promotes neuronal survival at dosages that inhibit activation of the c-Jun amino-terminal kinases (JNKs) in primary embryonic cultures and differentiated PC12 cells after trophic withdrawal and in mice treated with 1-methyl-4-phenyl tetrahydropyridine. In an effort to identify molecular target(s) of CEP-1347 in the JNK cascade, JNK1 and known upstream regulators of JNK1 were co-expressed in Cos-7 cells to determine whether CEP-1347 could modulate JNK1 activation. CEP-1347 blocked JNK1 activation induced by members of the mixed lineage kinase (MLK) family (MLK3, MLK2, MLK1, dual leucine zipper kinase, and leucine zipper kinase). The response was selective because CEP-1347 did not inhibit JNK1 activation in cells induced by kinases independent of the MLK cascade. CEP-1347 inhibition of recombinant MLK members in vitro was competitive with ATP, resulting in IC(50) values ranging from 23 to 51 nm, comparable to inhibitory potencies observed in intact cells. In addition, overexpression of MLK3 led to death in Chinese hamster ovary cells, and CEP-1347 blocked this death at doses comparable to those that inhibited MLK3 kinase activity. These results identify MLKs as targets of CEP-1347 in the JNK signaling cascade and demonstrate that CEP-1347 can block MLK-induced cell death.
The role of PKC epsilon in amyloid precursor protein (APP) processing was investigated using APP-overexpressing B103 cells. As reported previously, a PKC activator, phorbol-12,13-dibutyrate (PDBu), enhanced secretion of APP alpha, and this effect was blocked by a PKC inhibitor, GF109203X in this system. Selective inhibition of PKC epsilon by overexpressing the PKC epsilon V1 region, which binds specifically to the receptor for activated C-kinase (RACK), blocked PDBu-induced enhancement of APP alpha secretion as well as PDBu-induced decrease in beta-secretase-derived APP C-terminal fragment production. On the other hand, the level of PKC epsilon, but not that of PKC alpha or PKC gamma, was substantially lower in the brains of Alzheimer's disease patients compared to age-matched controls. These results add to a growing body of evidence that PKC epsilon plays an important role in modulating APP processing, and suggest that reduced PKC epsilon activity may contribute to the development of Alzheimer's disease.
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The pathogenic mechanism linking presenilin-1 (PS-1) gene mutations to familial Alzheimer's disease (FAD) is uncertain, but has been proposed to include increased neuronal sensitivity to degeneration and enhanced amyloidogenic processing of the beta-amyloid precursor protein (APP). We investigated this issue by using gene targeting with the Cre-lox system to introduce an FAD-linked P264L mutation into the endogenous mouse PS-1 gene, an approach that maintains normal regulatory controls over expression. Primary cortical neurons derived from PS-1 homozygous mutant knock-in mice exhibit basal neurodegeneration similar to their PS-1 wild-type counterparts. Staurosporine and Abeta1-42 induce apoptosis, and neither the dose dependence nor maximal extent of cell death is altered by the PS-1 knock-in mutation. Similarly, glutamate-induced neuronal necrosis is unaffected by the PS-1P264L mutation. The lack of effect of the PS-1P264L mutation is confirmed by measures of basal- and toxin-induced caspase and calpain activation, biochemical indices of apoptotic and necrotic signaling, respectively. To analyze the influence of the PS-1P264L knock-in mutation on APP processing and the development of AD-type neuropathology, we created mouse lines carrying mutations in both PS-1 and APP. In contrast to the lack of effect on neuronal vulnerability, cortical neurons cultured from PS-1P264L homozygous mutant mice secrete Abeta42 at an increased rate, whereas secretion of Abeta40 is reduced. Moreover, the PS-1 knock-in mutation selectively increases Abeta42 levels in the mouse brain and accelerates the onset of amyloid deposition and its attendant reactive gliosis, even as a single mutant allele. We conclude that expression of an FAD-linked mutant PS-1 at normal levels does not generally increase cortical neuronal sensitivity to degeneration. Instead, enhanced amyloidogenic processing of APP likely is critical to the pathogenesis of PS-1-linked FAD.
Recent evidence suggests potential associations between birthweight and disease in later life. For resource or other reasons recorded birthweight may be unavailable to researchers who have access to uniquely relevant outcome data. The present study examined the validity of parental recall of birthweight. Parents of 1015 males and females aged 12 and 15 years participating in the Young Hearts Study (a cluster random sample of 1015 males and females aged 12 and 15 years from post-primary schools in Northern Ireland) completed a questionnaire which included a question about their child's birthweight. The answer provided was compared with recorded birthweight obtained from archived computerised child health records with a cut-off point for inaccurate reporting set at +/- 227 g (1/2 lb). The influence of social class and weight at birth on accuracy of recall was also determined. A total of 84.8% of parents accurately recalled their child's birthweight to within 227 g. Parents from non-manual occupation social classes recalled birthweight more accurately than those from manual occupation social classes (88.0 vs. 82.6% accurate: chi2 = 4.81, p = 0.03). Parents of low birthweight infants tended to recall their birthweight less accurately than parents of normal weight infants: 76.1% accurate compared to 86.1% accurate: chi2 = 3.54, p = 0.06. Parents of high birthweight infants recalled their birthweight less accurately than parents of normal weight infants: 78.5% accurate: chi2 = 3.94, p = 0.05. In conclusion, parentally recalled birthweight may be a suitable proxy for recorded birthweight for population based research into disease in childhood and adolescence.
beta-Amyloid (Abeta) deposits are found in the brains of approximately one-third of patients who die within days after a severe head injury; their presence correlating strongly with possession of an apolipoprotein E (apoE)-epsilon4 allele. The aim of the study was to investigate the relationship between Abeta42, Abeta40 and apoE immunostaining of Abeta plaques in the cerebral cortex and the relevance of apoE genotype in 23 fatally head-injured patients. These cases were known to have Abeta deposits from a previous study in which they were examined and semiquantified and related to apoE genotype. In the present study, the temporal cortex was probed using four different antibodies that recognize Abeta42(43), Abeta40 and an antibody to apoE. Abeta42(43)-positive plaques were observed in all of the 23 cases and Abeta40 immunoreactivity in only 11 of the 23 cases. In addition, semiquantitative analysis showed that relatively fewer plaques were detected with anti-Abeta40 than anti-Abeta42(43). ApoE-immunoreactive plaques were identified in 18 of the 23 cases. The number of plaques stained for apoE was relatively less than for Abeta42(43) but greater than for Abeta40. Furthermore, the density of Abeta plaques detected using either Abeta42(43), Abeta40 or apoE antibodies was associated with possession of apoE-epsilon4 in an allele dose-dependent manner. The results are consistent with Abeta42(43) as the initially deposited species in brain parenchyma and provide evidence that apoE is involved in the early stages of amyloid deposition. Further, the findings may be of relevance to the role of apoE genotype in influencing outcome after acute brain injury.
The Alzheimer's disease amyloid peptide Abeta has a heterogeneous COOH terminus, as variants 40 and 42 residues long are found in neuritic plaques and are secreted constitutively by cultured cells. The proteolytic activity that liberates the Abeta COOH terminus from the beta-amyloid precursor protein is called gamma-secretase. It could be one protease with dual specificity or two distinct enzymes. By using enzyme-linked immunosorbent assays selective for Abeta40 or Abeta42, we have measured Abeta secretion by a HeLa cell line, and we have examined the dose responses for a panel of five structurally diverse gamma-secretase inhibitors. The inhibitors lowered Abeta and p3 secretion and increased levels of the COOH-terminal 99-residue beta-amyloid precursor protein derivative that is the precursor for Abeta but did not alter secretion of beta-amyloid precursor protein derivatives generated by other secretases, indicating that the inhibitors blocked the gamma-secretase processing step. The dose-dependent inhibition of Abeta42 was unusual, as the compounds elevated Abeta42 secretion at sub-inhibitory doses and then inhibited secretion at higher doses. A compound was identified that elevated Abeta42 secretion at a low concentration without inhibiting Abeta42 or Abeta40 at high concentrations, demonstrating that these phenomena are separable pharmacologically. Using either of two methods, IC50 values for inhibition of Abeta42 and Abeta40 were found to have the same rank-order and fall on a trend line with near-unit slope. These results favor the hypothesis that Abeta variants ending at residue 40 or 42 are generated by a single gamma-secretase.
BACKGROUND: For patients with metastatic prostate cancer, treatment is primarily palliative, relying mainly on the suppression of systemic androgen hormone levels. To help document the achievement of palliation and to characterize positive and negative effects of treatment, we evaluated quality-of-life (QOL) parameters in patients with metastatic prostate cancer who were randomly assigned to two methods of androgen deprivation. METHODS: Patients (n = 739) with stage M1 (bone or soft tissue metastasis) prostate cancer were enrolled in a QOL protocol that was a companion to Southwest Oncology Group INT-0105, a randomized double-blind trial comparing treatment with bilateral orchiectomy (surgical castration) plus either flutamide or placebo. Patients completed a comprehensive battery of QOL questionnaires at random assignment to treatment and at 1, 3, and 6 months later. Data were collected on three treatment-specific symptoms (diarrhea, gas pain, and body image), on physical functioning, and on emotional functioning. All P values are two-sided. RESULTS: Questionnaire return rates for this study never dropped below 80%; only 2% of the patients did not submit baseline QOL assessments. Cross-sectional analyses (corrected for multiple testing) identified statistically significant differences that favored orchiectomy plus placebo for two of the five primary QOL parameters as follows: patients receiving flutamide reported more diarrhea at 3 months (P = .001) and worse emotional functioning at 3 and 6 months (both P<.003). Longitudinal analyses replicated these findings. Other analyzed QOL parameters favored the group receiving placebo but were not statistically significant after adjustment for multiple testing. CONCLUSIONS: We found a consistent pattern of better QOL outcomes at each follow-up assessment during the first 6 months of treatment for orchiectomized patients with metastatic prostate cancer who received placebo versus flutamide. Improvement over time was evident in both treatment groups but more so for patients receiving placebo.
The effects of dietary cholesterol on brain amyloid precursor protein (APP) processing were examined using an APP gene-targeted mouse, genetically humanized in the amyloid beta-peptide (Abeta) domain and expressing the Swedish familial Alzheimer's disease mutations. These mice express endogenous levels of APP holoprotein and abundant human Abeta. Increased dietary cholesterol led to significant reductions in brain levels of secreted APP derivatives, including sAPPalpha, sAPPbeta, Abeta1-40, and Abeta1-42, while having little to no effect on cell-associated species, including full-length APP and the COOH-terminal APP processing derivatives. The changes in levels of sAPP and Abeta in brain all were negatively correlated with serum cholesterol levels and levels of serum and brain apoE. These results demonstrate that secreted APP processing derivatives and Abeta can be modulated in the brain of an animal by diet and provide evidence that cholesterol plays a role in the modulation of APP processing in vivo. APP gene-targeted mice lacking apoE, also have high serum cholesterol levels but do not show alterations in APP processing, suggesting that effects of cholesterol on APP processing require the presence of apoE.
Fibrillar amyloid deposits are defining pathological lesions in Alzheimer's disease brain and are thought to mediate neuronal death. Amyloid is composed primarily of a 39-42 amino acid protein fragment of the amyloid precursor protein (APP), called amyloid beta-protein (Abeta). Because deposition of fibrillar amyloid in vitro has been shown to be highly dependent on Abeta concentration, reducing the proteolytic release of Abeta is an attractive, potentially therapeutic target. Here, the turnover rate of brain Abeta has been determined to define treatment intervals over which a change in steady-state concentration of Abeta could be measured. Mice producing elevated levels of human Abeta were used to determine approximate turnover rates for Abeta and two of its precursors, C99 and APP. The t1/2 for brain Abeta was between 1.0 and 2.5 hr, whereas for C99, immature, and fully glycosylated forms of APP695 the approximate t1/2 values were 3, 3, and 7 hr, respectively. Given the rapid Abeta turnover rate, acute studies were designed using phorbol 12-myristate 13-acetate (PMA), which had been demonstrated previously to reduce Abeta secretion from cells in vitro via induction of protein kinase C (PKC) activity. Six hours after intracortical injection of PMA, Abeta levels were significantly reduced, as measured by both Abeta40- and Abeta42-selective ELISAs, returning to normal by 12 hr. An inactive structural analog of PMA, 4alpha-PMA, had no effect on brain Abeta levels. Among the secreted N-terminal APP fragments, APPbeta levels were significantly reduced by PMA treatment, whereas APPalpha levels were unchanged, in contrast to most cell culture studies. These results indicate that Abeta is rapidly turned over under normal conditions and support the therapeutic potential of elevating PKC activity for reduction of brain Abeta.
Fatal head injury results in the formation of diffuse parenchymal deposits of amyloid beta-protein (A beta) in the brains of approximately 30% of individuals. We used carboxyl terminal-specific antisera to examine the exact nature of these deposits in paraffin sections of neocortex from seven head-injured patients. Immunostaining for A beta 42 was observed in all parenchymal deposits whereas staining for A beta 40, the form of the protein which predominates in serum and cerebrospinal fluid, was seen in only a small proportion of deposits. The relative paucity of A beta 40 suggests that post-traumatic deposits do not arise as a result of passive leakage from damaged cerebral blood vessels but are similar to the early A beta 42 parenchymal deposits seen in Down's syndrome and Alzheimer's disease.
The purpose of this study was to analyze the relationships between physical activity (ACT), including sports participation (SP) and antecedent risk factors for coronary heart disease (CHD), in a representative sample of adolescents from Northern Ireland, a region of high coronary mortality. Biological and behavioral risk factors were measured in a random sample of 1015 school children aged 12 and 15 yr. ACT and SP were assessed by self-report questionnaire, and relationships with biological risk factors were analyzed with stepwise multiple linear regression after controlling for potential confounders. Results showed that in 15-yr-old males ACT was beneficially associated with systolic blood pressure (P < 0.05), lipid profile, and cardiorespiratory fitness (both P < 0.01). In 15-yr-old females, SP was associated beneficially with fatness and cardiorespiratory fitness. Odds ratios calculated from logistic regression revealed that for the older children, a relatively small drop (-20%) in ACT (boys) or SP (girls) was significantly related to the probability of exposure to multiple risk factors. Overall, relationships were stronger for males rather than females and for older rather than younger children. This study provides further evidence for beneficial associations between ACT, SP, and CHD risk status in adolescents.
The processing of the beta-amyloid precursor protein (APP) in vivo has been characterized in a novel animal model that recapitulates, in part, the APP genotype of a familial form of Alzheimer's disease (AD). A gene-targeting strategy was used to introduce the Swedish familial AD mutations and convert mouse Abeta to the human sequence. The mutant APP is expressed at normal levels in brain, and cleavage at the mutant beta-secretase site is both accurate and enhanced. Furthermore, human Abeta production is significantly increased to levels 9-fold greater than those in normal human brain while nonamyloidogenic processing is depressed. The results on Abeta production extend similar findings obtained in cell culture to the brain of an animal and substantiate Abeta as a etiological factor in Swedish familial AD. These animals provide several distinguishing features over others created by conventional transgenic methodologies. The spatial and temporal expression patterns of human Abeta are expected to be faithfully reproduced because the gene encoding the mutant APP remains in its normal chromosomal context. Thus, the neuropathological consequences of human Abeta overproduction can be evaluated longitudinally in the absence of potential mitigating effects of APP overexpression or presence of the mouse Abeta peptide.
Recent studies have demonstrated the deposition of amyloid beta (A beta) protein with carboxyl- and aminoterminal heterogeneity in cortical and cerebrovascular deposits of Alzheimer's disease (AD). Using carboxyl end-terminal specific antibodies to A beta peptides, we examined the immunocytochemical distribution of A beta 40 and A beta 42 species in brain tissue from a Swedish subject with familial AD (FAD) bearing the double mutation at codons 670/671 in the amyloid beta precursor protein (A beta PP), and from subjects with Down's syndrome and sporadic AD. In the Swedish subject, we found profound parenchymal A beta deposits and cerebral amyloid angiopathy in all four cortical lobes and cerebellum. A beta 42 was evident in almost all parenchymal deposits as well as many vascular deposits. Although A beta 40 was present in meningeal and intraparenchymal vessels, deposits containing this shorter peptide reactivity were sparse. Surprisingly, our observations in Swedish FAD showing a remarkable abundance of A beta 42 in both parenchymal and vascular deposits were qualitatively similar to the Down's syndrome and most sporadic AD cases, and to previously published A beta PP717 FAD. While previous transfection studies in different cell cultures indicate substantially increased soluble A beta production and A beta 40 species to be predominant, it would appear that the double A beta PP mutations in Swedish FAD largely result in the deposition of the longer A beta 42 in vivo.
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Amyloid deposits in Alzheimer's disease, Down's syndrome and aged brain are composed largely of A beta protein, which is generated by proteolytic processing of beta-amyloid precursor protein. Proteases responsible for liberating the A beta protein from the precursor have not yet been identified. Here, we examined the ability of cathepsin G, a chymotrypsin-like protease, to cleave two protease substrates: (i) a fluorogenic hexapeptide, whose sequence spans the cleavage site in the precursor for generating the A beta NH2-terminus, and (ii) recombinant human beta-amyloid precursor protein purified from a baculovirus expression system. Unlike two other members of the chymotrypsin family, cathepsin G readily degraded the hexapeptide. Furthermore, cathepsin G cleaved the beta-amyloid precursor protein to generate several breakdown products, including a prominent 11,500 mol. wt fragment immunoreactive with antibodies directed against the COOH-terminus of the protein. This COOH-terminal fragment co-migrated using two-dimensional isoelectric focusing/sodium dodecyl sulfate-polyacrylamide gel electrophoresis with C-100, a recombinant COOH-terminal segment of the beta-amyloid precursor, whose NH2-terminus is one residue upstream of the NH2-terminus of the A beta domain. We also examined the localization of cathepsin G in human brain. The distribution of cathepsin G-containing cells was examined by immunohistochemistry in the temporal cortex of both Alzheimer's and aged control samples. Cathepsin G-like immunoreactivity was contained specifically within neutrophils. As visualized by double-labeling with antibodies to cathepsin G and Factor VIII, neutrophils were most frequently found within meningeal or cortical blood vessels. In addition, occasional neutrophils could be identified without an apparent vascular surround, in the brain parenchyma. By simultaneous labeling with antibodies to cathepsin G and A beta protein, neutrophils were also sometimes found associated with both parenchymal and vessel amyloid deposits; however, these associations were rare. These findings indicate that cathepsin G is capable of cleaving the beta-amyloid precursor protein to liberate the free NH2-terminus of the A beta protein and may have access to areas where this material is deposited in Alzheimer's disease. However, since there is no physical association between neutrophils and deposited amyloid and no increase in the number of neutrophils in an Alzheimer's brain, cathepsin G seems to be an unlikely mediator of amyloid deposition in this disease.