On the compartmentalization of catalase,fatty acyl-CoA oxidase and urate oxidase in mammalian livers,and the influence of clofibrate treatment on this microlocalization

The compartmentalization of catalase, fatty acyl-CoA oxidase and urate oxidase was examined in the livers of mice, rats and guinea pigs, using the technique of digitonin extraction in order to avoid the trauma associated with centrifugation procedures. The results are interpreted as indicating that an appreciable proportion of catalase activity occurs in the cytoplasmic compartment of these cells. Following treatment of the animals with clofibrate, the specific activity in both peroxisomal and cytoplasmic compartments was increased, with a higher proportion of cytoplasmic catalase being evident in mice. The results for catalase were compared with those for fatty acyl-CoA oxidase and urate oxidase both of which were indicated as showing a closer association with the peroxisomal compartment than was the case for catalase. These data have been discussed in relation to their significance on present understanding of peroxisomal structure and function.     

Peripheral inflammatory biomarkers are associated with cognitive function and dementia: Framingham Heart Study Offspring cohort

Inflammatory protein biomarkers induced by immune responses have been associated with cognitive decline and the pathogenesis of Alzheimer's disease (AD). Here, we investigate associations between a panel of inflammatory biomarkers and cognitive function and incident dementia outcomes in the well-characterized Framingham Heart Study Offspring cohort. Participants aged ≥40 years and dementia-free at Exam 7 who had a stored plasma sample were selected for profiling using the OLINK proteomics inflammation panel. Cross-sectional associations of the biomarkers with cognitive domain scores (N = 708, 53% female, 22% apolipoprotein E (APOE) ε4 carriers, 15% APOE ε2 carriers, mean age 61) and incident all-cause and AD dementia during up to 20 years of follow-up were tested. APOE genotype-stratified analyses were performed to explore effect modification. Higher levels of 12 and 3 proteins were associated with worse executive function and language domain factor scores, respectively. Several proteins were associated with more than one cognitive domain, including IL10, LIF-R, TWEAK, CCL19, IL-17C, MCP-4, and TGF-alpha. Stratified analyses suggested differential effects between APOE ε2 and ε4 carriers: most ε4 carrier associations were with executive function and memory domains, whereas most ε2 associations were with the visuospatial domain. Higher levels of TNFB and CDCP1 were associated with higher risks of incident all-cause and AD dementia. Our study found that TWEAK concentration was associated both with cognitive function and risks for AD dementia. The association of these inflammatory biomarkers with cognitive function and incident dementia may contribute to the discovery of therapeutic interventions for the prevention and treatment of cognitive decline.     

The biogenesis protein PEX14 is an optimal marker for the identification and localization of peroxisomes in different cell types, tissues, and species in morphological studies

Catalase and ABCD3 are frequently used as markers for the localization of peroxisomes in morphological experiments. Their abundance, however, is highly dependent on metabolic demands, reducing the validity of analyses of peroxisomal abundance and distribution based solely on these proteins. We therefore attempted to find a protein which can be used as an optimal marker for peroxisomes in a variety of species, tissues, cell types and also experimental designs, independently of peroxisomal metabolism. We found that the biogenesis protein peroxin 14 (PEX14) is present in comparable amounts in the membranes of every peroxisome and is optimally suited for immunoblotting, immunohistochemistry, immunofluorescence, and immunoelectron microscopy. Using antibodies against PEX14, we could visualize peroxisomes with almost undetectable catalase content in various mammalian tissue sections (submandibular and adrenal gland, kidney, testis, ovary, brain, and pancreas from mouse, cat, baboon, and human) and cell cultures (primary cells and cell lines). Peroxisome labeling with catalase often showed a similar tissue distribution to the mitochondrial enzyme mitochondrial superoxide dismutase (both responsible for the degradation of reactive oxygen species), whereas ABCD3 exhibited a distinct labeling only in cells involved in lipid metabolism. We increased the sensitivity of our methods by using QuantumDots?, which have higher emission yields compared to classic fluorochromes and are unsusceptible to photobleaching, thereby allowing more exact quantification without artificial mistakes due to heterogeneity of individual peroxisomes. We conclude that PEX14 is indeed the best marker for labeling of peroxisomes in a variety of tissues and cell types in a consistent fashion for comparative morphometry.     

Quinone interaction with the respiratory chain-linked NADH dehydrogenase of beef heart mitochondria. II. Duroquinone reductase activity

1. Enzymatic reduction of 2,3,5,6-tetramethyl-1,4-benzoquinone (duroquinone) by NADH can be used in an assay procedure for the NADH dehydrogenase. The reduction of this quinone occurs in the region of the electron transport system between the primary dehydrogenase and the cytochrome system as defined by the almost complete loss of reductase activity following piericidin A treatment.

2. Duroquinone reduction can be distinguished from ubiquinone 2 reduction by the marked inhibition of the former following phospholipase C, poly- -lysine, or chloroquine diphosphate treatment. In addition, duroquinone reduction requires the presence of endogenous ubiquinone 10 specifically whereas ubiquinone 2 reduction does not require the presence of endogenous quinone. These observations are consistent with the nonequivalency of the reduction sites of duroquinone and ubiquinone 2.

3. Duroquinol can be utilized as an electron donor for the energy-linked reduction, of NAD⁺. Duroquinol reduction of NAD⁺ is dependent upon the presence of ATP, is inhibited by oligomycin, carbonyl cyanide p-trifluoro methoxyphenylhydrazone and piericidin A, and is not inhibited by antimycin A at levels which inhibit electron transport.

4. Duroquinone reduction as well as ubiquinone 2 reduction are inhibited almost completely by phospholipase A, p-chloromercuribenzoate, o-phenanthroline, and Triton X100 treatments.