Aging-associated reductions in AMP-activated protein kinase activity and mitochondrial biogenesis

Recent studies have demonstrated a strong relationship between aging-associated reductions in mitochondrial function, dysregulated intracellular lipid metabolism, and insulin resistance. Given the important role of the AMP-activated protein kinase (AMPK) in the regulation of fat oxidation and mitochondrial biogenesis, we examined AMPK activity in young and old rats and found that acute stimulation of AMPK-alpha(2) activity by 5'-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR) and exercise was blunted in skeletal muscle of old rats. Furthermore, mitochondrial biogenesis in response to chronic activation of AMPK with beta-guanidinopropionic acid (beta-GPA) feeding was also diminished in old rats. These results suggest that aging-associated reductions in AMPK activity may be an important contributing factor in the reduced mitochondrial function and dysregulated intracellular lipid metabolism associated with aging.     

Autonomy of cell proliferation and developmental programs during Arabidopsis aboveground organ morphogenesis

Elaboration of size and shape in multicellular organisms involves coordinated cell division and cell growth. In higher plants, continuity of cell layer structures exists from the shoot apical meristem (SAM), where organ primordia arise, to mature aboveground organs. To unravel the extent of inter-cell layer coordination during SAM and aboveground organ development, cell division in the epidermis was selectively restricted by expressing two cyclin-dependent kinase inhibitor genes, KRP1/ICK1 and KRP4, driven by the L1 layer-specific AtML1 promoter. The transgenes conferred reduced plant size with striking, distorted lateral organ shape. While epidermal cell division was severely inhibited with compensatory cell size enlargement, the underlying mesophyll/cortex layer kept normal cell numbers and resulted in small, packed cells with disrupted cell files. Our results demonstrate the autonomy of cell number checkpoint in the underlying tissues when epidermal cell division is restricted. Finally, the L1 layer-specific expression of both KRP1/ICK1 and KRP4 showed no effects on the structure and function of the SAM, suggesting that the effects of these cyclin-dependent kinase inhibitors are context dependent.     

Alanine scanning mutational analysis of the ligand binding pocket of the human Vitamin D receptor

We achieved exhaustive alanine scanning mutational analysis of the amino acid residues lining the ligand binding pocket of the Vitamin D receptor to investigate the mechanism of the ligand recognition by the receptor. This is the first exhaustive analysis in the nuclear receptor superfamily. Our results demonstrated the role and importance of all the residues lining the ligand binding pocket. In addition, this analysis was found to indicate ligand-specific ligand-protein interactions, which have key importance in determining the transactivation potency of the individual ligands. Thus, the analysis using 1beta-methyl-1alpha,25-dihydroxyvitamin D(3) revealed the specific van der Waals interactions of 1beta-methyl group with the receptor.     

Identification of (Na,K)ATPase inhibitor in brine shrimp,Artemia salina,as long-chain fatty acids

Summary An inhibitory activity to (Na,K)ATPase was found in cell extracts of the brine shrimp, Artemia salina, irrespective of its developmental stages. Organic solvent extraction together with gas chromatographic analysis reveals that the inhibitory activity is due to long-chain, non-esterified fatty acids and their derivatives. Unsaturated fatty acids, especially with cis-configuration, are more effective in inhibition than saturated ones.Abbreviations ATPase adenosine triphosphatase - EDTA ethylenediamine-tetraacetate - TLC thin-layer chromatography     

A novel MHC class I-related molecule expressed on mouse thymic stroma cells and mature lymphocytes

A monoclonal antibody (mAb) TP-3 has been established by immunizing rats with the BALB/c mouse thymic epithelial cell line TEL-2. The TP-3 antigen is expressed on stroma cells of thymus, spleen, and lymph node in syngeneic BALB/c mice (H-2 ^d ). This antigen is also expressed at a low level on the cell surface of immature thymocytes, and at a high level on mature T and B cells. In allogeneic mice such as C57BL/6 (H-2 ^b ) or C3H (H-2 ^k ), no cells expressed the TP-3 antigen. Using H-2 congenic mice, reactivity with mAb TP-3 was found to map to a region of H-2D ^d L ^d or between D ^d and Qa, suggesting that TP-3 is a major histocompatibility complex (MHC) class I antigen. However, immunoprecipitation analysis indicated that this antigen is not identical to the classical mouse class I molecules in terms of molecular size, antigenicity, and tissue distribution.     

Parallel evolution in radiation ofOhomopterus ground beetles inferred from mitochondrial ND5 gene sequences

Molecular phylogenetic analyses using mitochondrial NADH dehydrogenase subunit 5 (ND5) gene sequences representing all 15 species and the majority of subspecies or races of theOhomopterus ground beetles from all over the Japanese archipelago have uncovered a remarkable evolutionary history. Clustering of the species in the molecular phylogenetic tree is linked to their geographic distribution and does not correlate with morphological characters. Taxonomically the same species or the members belonging to the same species-group fall out in more than two different places on the ND5 tree. Evidence has been presented against a possible participation of ancestral polymorphism and random lineage sorting or of hybrid individuals for the observed distribution of mitochondrial DNA haplotypes. The most plausible explanation of our results is that parallel evolution took place in different lineages. Most notably,O. dehaanii, O. yaconinus, andO. japonicus in a lineage reveal almost identical morphology with those of the same species (or subspecies) but belonging to the phylogenetically remote lineages.The nucleotide sequence data reported in this paper will appear in the DDBJ, EMBL, and GenBank nucleotide sequence databases with accession numbers D50711-DD-50733 and D87131-D87186.     

Quantitative determination of disopyramide, verapamil and flecainide enantiomers in rat plasma and tissues by high-performance liquid chromatography

Enantiomers of disopyramide (DP), flecainide (FLC) and verapamil (VP) were extracted from rat plasma and tissues (brain, lung, heart, liver, kidney and muscle), followed by quantitative determination using enantioselective high-performance liquid chromatography with chiral stationary-phase columns. The recoveries of S-(+)- and R-(−)-DP from tissues were higher than 69%, and the within- and between-day coefficients of variation were very low (0.5 – 5.7%). The lower limits of detection in each tissue were less than 289 ng/g tissue. The recoveries of S-(+)- and R-(−)-FLC from tissues were higher than 88%, and the within- and between-day coefficients of variation were 1.2–6.0%. The lower limits of detection in each tissue were less than 37 ng/g tissue. The recoveries of S-(−)- and R-(+)-VP from tissues were higher than 80%, and the within- and between-day coefficients of variation were 0.5–6.2%. The lower limits of detection in each tissue were less than 51 ng/g tissue. The analytical methods established in this study will be suitable for determining the concentrations of the enantiomers of these anti-arrhythmic agents in rat plasma and tissues.