Cross-Sectional and Longitudinal Comparison of Tau Imaging with 18F-MK6240 and 18F-Flortaucipir in Populations Matched for Age, MMSE and Brain Beta-Amyloid Burden.

OBJECTIVES: Longitudinal tau quantification may provide a useful marker of drug efficacy in clinical trials. Different tau PET tracers may have different sensitivity to longitudinal changes, but without a head-to-head dataset or a carefully designed case-matching procedure, comparing results in different cohorts can be biased. In this study, we compared the tau PET tracers, 18F-MK6240 and 18F-flortaucipir (FTP), both cross-sectionally and longitudinally by case-matching subjects in the AIBL and ADNI longitudinal cohort studies. METHODS: A subset of 113 participants from AIBL and 113 from ADNI imaged using 18F-MK6240 and 18F-FTP respectively, with baseline and follow-up, were matched based on baseline clinical diagnosis, MMSE, age and amyloid (Aß) PET centiloid value. Subjects were grouped as 64 Aß- cognitively unimpaired (CU), 22 Aß+ CU, 14 Aß+ mild cognitive impairment (MCI) and 13 Aß+ Alzheimer's disease (AD). Tracer retention was measured in the mesial, temporoparietal, rest of the cortex, and a meta-temporal region composed of entorhinal, inferior/middle temporal, fusiform, parahippocampus and amygdala. T-tests were employed to assess group separation at baseline using SUVR Z-scores and longitudinally using SUVR%/Yr. RESULTS: Both tracers detected statistically significant differences at baseline in most regions between all clinical groups. Only 18F-MK6240 showed statistically significant higher rate of SUVR increase in Aß+ CU compared to Aß- CU in the mesial, meta-temporal and temporoparietal regions. CONCLUSION: 18F-MK6240 appears to be a more sensitive tracer for change in tau level at the preclinical stage of AD.

'I'm not trusted in the kitchen': food environments and food behaviours of young people attending school and college.

BACKGROUND: Food behaviours are important in the context of health and obesity. The aim was to explore the environments and food behaviours of a sample of young people in the North East of England to further understanding of the relationship between eating behaviours and environmental context. METHODS: Focus groups were conducted with four groups of young people aged 16-20 years (n = 40; 28 male, 12 female) between November 2006 and June 2007. Analysis was informed by grounded theory methods and was an iterative process of identifying themes across the transcripts. RESULTS: Topics explored included: their main environment, home food responsibility and cooking, food outside of the home, where food was purchased/obtained and where food was eaten and with whom. Emergent themes included: the value for money in food purchases, time convenience, the car as a means of accessing food and health perceptions. CONCLUSIONS: The complexities of the food environment were illustrated. This work has highlighted the importance of the home food environment and parents, and indicated the importance of factors such as time and cost in this age group's food choices. The behavioural norms around food behaviours merit further exploration for this population in transition between adolescence and adulthood.

Exploring the "bisexual bridge": a qualitative study of risk behavior and disclosure of same-sex behavior among black bisexual men.

OBJECTIVES: We explored factors influencing sexual behavior, disclosure of same-sex behavior, and condom-use practices among Black bisexual men. METHODS: We conducted semistructured interviews with 38 Black men in Atlanta, Georgia, who reported having had oral, vaginal, or anal sex with both men and women in the prior 6 months. RESULTS: Participants described approaches to disclosure of same-sex behavior as part of a complex decisional balance influenced by both situational and individual factors and ranging from full disclosure to total secrecy. Influences on sexual behavior and condom-use practices included: (1) type of relationship, (2) gender-specific considerations, (3) perceptions of comfort or trust, and (4) fear of disease or pregnancy. CONCLUSIONS: Disclosure of same-sex behavior was not a major influence on the sexual behavior and condom-use practices of the Black bisexual men in our study, who demonstrated heterogeneity in approaches to sexual behavior, disclosure of same-sex behavior, and condom-use practices. Additional research is needed to assess the social determinants of sexual risk for this population. Future HIV-prevention efforts should include initiatives to encourage accuracy in risk assessment and in taking sexual histories in clinical settings.

Potential protection of skin by acute UVA irradiation--from cellular to animal models.

The UVA (320-380 nm) component of sunlight has oxidizing properties which may be deleterious to skin cells and tissue but can also lead to the strong up-regulation of the heme-catabolizing enzyme, heme oxygenase-1. This enzyme has well-established antioxidant actions in cells as well as anti-inflammatory properties in mammals. There is also evidence from rodent models that this enzyme is responsible for the UVA-mediated protection against UVB-induced immunosuppression that occurs in skin. The relevance of these findings to acute and chronic effects of sunlight including skin carcinogenesis is currently under investigation as are the potential implications for sunlight protection in humans.

Solar ultraviolet A radiation: an oxidizing skin carcinogen that activates heme oxygenase-1.

Ultraviolet A (UVA: 320-380 nm) radiation is an oxidizing carcinogen that has proved an ideal agent for demonstrating the oxidant inducibility of the mammalian heme oxygenase-1 (HO-1) gene. The UVA response in cultured human skin fibroblasts and other cell types is mediated by singlet oxygen and is strongly influenced by cellular reducing equivalents. Free heme, an entity that can be generated by UVA irradiation of cells, also appears to be a critical intermediate that can directly influence both the transcriptional activation and repression of the HO-1 gene. Heme release is likely to be of central importance to the inflammatory response in skin and its abrogation by HO.

Development and validation of a stability-indicating HPLC method for the simultaneous determination of losartan potassium, hydrochlorothiazide, and their degradation products.

Losartan potassium was the first in a new class of potent angiotensin II receptor antagonists which are well-tolerated in the treatment of hypertension. Losartan potassium is the active ingredient in tablets COZAAR and is combined with diuretic co-active hydrochlorothiazide (HCTZ) in tablets HYZAAR for increased efficacy. Losartan potassium has one main impurity and two primary degradates. HCTZ has one major degradate as well as two common process impurities. Historically, separate methods have been used for the analysis of each active and their respective impurities and degradates. The ultimate goal of this work was to develop and validate a single high-performance liquid chromatography method selective for the eight main components of tablets HYZAAR. A single method was developed to afford simultaneous quantitation of actives and degradates for each of the two existing formulations. Each method is presented herein and demonstrated to be suitable for quantitation to 0.1% levels of all relevant degradates, as well as 100% levels of respective drug substances.

Purification and identification of an impurity in bulk hydrochlorothiazide.

Hydrochlorothiazide (6-chloro-3,4-dihydro-2H-1,2,4-benzothiadiazine-7-sulfonamide 1,1-dioxide) (HCTZ) 1 is a widely used diuretic and anti-hypertensive. Recently, the Pharmeuropa recognized a new impurity initially thought to be an HCTZ dimer 6, which consists of the active drug (HCTZ) linked via the former beta-ring methylene to a known degradate, 5-chloro-2,4-disulfamylaniline 2. In an effort to meet a new requirement, an analytical high-pressure liquid chromatography method was developed that was selective and sensitive to the subject impurity. The impurity was concentrated and purified using a combination of solid phase extraction and reverse-phase high-pressure liquid chromatography. Subsequently, the impurity has been identified as a specific HCTZ-CH2-HCTZ isomer utilizing a variety of analytical techniques, including hydrolysis, ultraviolet spectroscopy, liquid chromatography/mass spectrometry, and 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. The data resulting from the application of these analytical techniques confirm the identity of the impurity as a methylene bridged pair of HCTZ molecules; however, a total of six possible isomers 7a-f exist because of the presence of three reactive amines/sulfonamides on each HCTZ molecule. One unique molecular structure (4-[[6-chloro-3,4,-dihydro-2H-1,2,4-benzothiadiazine-7-sulfonamide-1,1-dioxide]-methyl]-chloro-3-hydro-H-1,2,4-benzothiadiazine-7-sulfonamide-1,1-dioxide) 7f was identified using two-dimensional COSY, NOESY, and TOCSY 1H NMR experiments.

Tea flavonoids and cardiovascular health.

Tea is rich in antioxidant polyphenols (catechins, flavonols, theaflavins and thearubigins). Epidemiological evidence relating regular consumption of tea or related polyphenols to CHD is equivocal. Catechins are absorbed from tea, but low plasma concentrations are attained. The bioavailability of theaflavins and thearubigins is unknown. Tea does not reduce blood pressure or plasma lipids in well-controlled human trials. Tea polyphenols inhibit LDL lipid peroxidation in vitro, but the effect ex vivo is small. The plasma antioxidant potential increases after drinking green but not black tea. Tea consumption tended to reduce the development of aortic atherosclerosis in rabbits. Tea polyphenols exert marked effects on cells, and inhibit neutrophil migration and inflammatory responses, sometimes at low concentrations. These diverging results suggest potential beneficial effects, but emphasize the need for good human trials of tea using early markers of CHD before firm conclusions can be drawn.

Epicatechin and its in vivo metabolite, 3'-O-methyl epicatechin, protect human fibroblasts from oxidative-stress-induced cell death involving caspase-3 activation.

There is considerable current interest in the cytoprotective effects of natural antioxidants against oxidative stress. In particular, epicatechin, a major member of the flavanol family of polyphenols with powerful antioxidant properties in vitro, has been investigated to determine its ability to attenuate oxidative-stress-induced cell damage and to understand the mechanism of its protective action. We have induced oxidative stress in cultured human fibroblasts using hydrogen peroxide and examined the cellular responses in the form of mitochondrial function, cell-membrane damage, annexin-V binding and caspase-3 activation. Since one of the major metabolites of epicatechin in vivo is 3'-O-methyl epicatechin, we have compared its protective effects with that of epicatechin. The results provide the first evidence that 3'-O-methyl epicatechin inhibits cell death induced by hydrogen peroxide and that the mechanism involves suppression of caspase-3 activity as a marker for apoptosis. Furthermore, the protection elicited by 3'-O-methyl epicatechin is not significantly different from that of epicatechin, suggesting that hydrogen-donating antioxidant activity is not the primary mechanism of protection.

An HPLC method to detect heme oxygenase activity.

This unit presents a method to calculate heme oxygenase enzymatic activity from the formation of bilirubin equivalents [biliverdin-Ix alpha (BV) and bilirubin-IX alpha (BR)]. The BV and BR generated in the reaction are separated by reversed-phase HPLC and detected using visible absorbance spectroscopy. Since both metabolites of heme degradation are directly quantifiable, the assay eliminates the requirement for biliverdin reductase supplementation.

Heme oxygenase activity causes transient hypersensitivity to oxidative ultraviolet A radiation that depends on release of iron from heme.

Heme oxygenase (HO) breaks down heme to iron, biliverdin, and carbon monoxide, and activity of this enzyme increases in many tissues and cell types after exposure to oxidative stress. There is evidence that increased HO activity is involved in long-term protective mechanisms against oxidative stress. We studied the effect of artificially overexpressed HO activity on the cytotoxicity of oxidative ultraviolet A (UVA) radiation after loading human cells with the HO substrate ferric heme (hemin). In contrast to the reported long-term protection attributed to HO activity, cells overexpressing HO activity were hypersensitive to UVA radiation shortly after heme treatment when compared with control cells. Cells overexpressing HO activity showed an increased rate of heme consumption and a higher level of accumulated free chelatable iron when compared with control cells. The hypersensitivity of cells overexpressing HO to UVA radiation after heme treatment was apparently caused by the increased accumulation of chelatable iron, because the iron chelator desferrioxamine strongly reduced the hypersensitivity. One day after the heme treatment, cells overexpressing HO activity were no longer hypersensitive to UVA radiation. We conclude that increased HO activity can temporarily increase the sensitivity of cells to oxidative stress by releasing iron from heme.

Liquid chromatography-mass spectrometry and proton nuclear magnetic resonance characterization of trace level condensation products formed between lactose and the amine-containing diuretic hydrochlorothiazide.

Trace levels of condensation products between lactose and the amine-containing diuretic hydrochlorothiazide are formed when a mixture of the two solids containing 30% weight water is heated at 60 degrees C for 2 weeks. The two most abundant condensation products were characterized by liquid chromatography-mass spectrometry (LC-MS) and proton nuclear magnetic resonance ((1)H NMR) spectroscopy. Under these relatively mild conditions of formation, the amine-lactose reaction products are limited to those involving the elimination of only a single molecule of water, rather than the multiple-water eliminations associated with later stages of the Maillard reaction. The spectroscopic data clearly show that the primary condensation products are cyclic N-substituted glycosylamines rather than Schiff base, 1,2-enolic forms, or Amadori rearrangement products of identical mass. In solution, the two most abundant N-substituted glycosylamines are shown to be in a kinetically slow equilibrium with each other, most likely through a mutarotation involving the intermediate formation of the acyclic Schiff base.

Modulation of c-jun and c-fos transcription by UVB and UVA radiations in human dermal fibroblasts and KB cells.

We have previously demonstrated that the oxidizing component of ultraviolet-A (UVA) plays a central role in the activation of the nuclear oncogene and transcription factor, c-fos, in cultured human skin fibroblasts. We have now shown that expression of both c-jun and c-fos (AP-1) family of transcription factors is modulated by short and long wavelength solar ultraviolet (UV) radiation in human fibroblasts and human KB cells. UVA radiation activated c-jun and c-fos in both fibroblasts and KB cells, whereas ultraviolet-B (UVB) radiation activates such oncogenes only in KB cells. Moreover, decreasing the intracellular levels of reducing equivalents in human fibroblasts by glutathione (GSH) depletion lowered the UVA dose threshold for c-jun and c-fos activation several-fold and greatly amplified the UVA-mediated activation of such genes. A more modest effect was observed in GSH-depleted KB cells. In both GSH-depleted fibroblasts and KB cells, UVB radiation failed to amplify c-jun and c-fos activation indicating that the oxidative component of UVB plays a minor role in the modulation of such oncogene expression. These findings clearly indicate that both c-jun and c-fos are activated by the oxidizing component of UVA radiation in human fibroblasts and KB cells, while UVB-mediated modulation seems to be restricted to human epithelial cells and does not involve oxidizing intermediates.

The heme synthesis and degradation pathways: role in oxidant sensitivity. Heme oxygenase has both pro- and antioxidant properties.

The heme biosynthetic and catabolic pathways generate pro- and antioxidant compounds, and consequently, influence cellular sensitivity to oxidants. Heme precursors (delta-aminolevulinic acid, porphyrins) generate reactive oxygen species (ROS), from autoxidation and photochemical reactions, respectively. Heme, an essential iron chelate, serves in respiration, oxygen transport, detoxification, and signal transduction processes. The potential toxicity of heme and hemoproteins points to a critical role for heme degradation in cellular metabolism. The heme oxygenases (HOs) provide this function and participate in cellular defense. This hypothesis emerges from the observation that the activation of HO-1 is an ubiquitous cellular response to oxidative stress. The reaction products of HO activity, biliverdin, and its subsequent metabolite bilirubin, have antioxidant properties. Furthermore, iron released from HO activity stimulates ferritin synthesis, which ultimately provides an iron detoxification mechanism that may account for long-term cytoprotection observed after HO induction. However, such models have overlooked potential pro-oxidant consequences of HO activity. The HO reaction releases iron, which could be involved in deleterious reactions that compete with iron reutilization and sequestration pathways. Indeed, the induction of HO activity may have both pro- and antioxidant sequelae depending on cellular redox potential, and the metabolic fate of the heme iron.