Detection of 1270 nm emission from singlet oxygen and photocytotoxic property of sugar-pendant 60 fullerenes

Sugar-pendant [60] fullerene derivatives have been prepared from carbohydrate-linked azides 1a-e. Both monosugar (4a-e) and bissugar derivatives (5a-e) produce singlet oxygen ((1)O(2)) under laser irradiation (355 nm) proved by the direct observation of (1)O(2) emission at 1270 nm. Monosugar derivatives exhibit photocytotoxicity varying by the attached sugar molecule.     

Emergence of rules in cell society: Differentiation, hierarchy, and stability

A dynamic model for cell differentiation, where cells with internal chemical reaction dynamics interact with each other and replicate was studied. It led to spontaneous differentiation of cells and determination, as discussed in the isologous diversification. The following features of the differentiation were obtained: (1) hierarchical differentiation from a ’stem’ cell to other cell types, with the emergence of the interaction-dependent rules for differentiation; (2) global stability of an ensemble of cells consisting of several cell types, that were sustained by the emergent, autonomous control on the rate of differentiation; (3) existence of several cell colonies with different cell-type distributions. The results provide a novel viewpoint on the origin of a complex cell society, while relevance to some biological problems, especially to the hemopoietic system, is also discussed.     

Identification of target genes conferring ethanol stress tolerance to Saccharomyces cerevisiae based on DNA microarray data analysis

During industrial production process using yeast, cells are exposed to the stress due to the accumulation of ethanol, which affects the cell growth activity and productivity of target products, thus, the ethanol stress-tolerant yeast strains are highly desired. To identify the target gene(s) for constructing ethanol stress tolerant yeast strains, we obtained the gene expression profiles of two strains of Saccharomyces cerevisiae, namely, a laboratory strain and a strain used for brewing Japanese rice wine (sake), in the presence of 5% (v/v) ethanol, using DNA microarray. For the selection of target genes for breeding ethanol stress tolerant strains, clustering of DNA microarray data was performed. For further selection, the ethanol sensitivity of the knockout mutants in each of which the gene selected by DNA microarray analysis is deleted, was also investigated. The integration of the DNA microarray data and the ethanol sensitivity data of knockout strains suggests that the enhancement of expression of genes related to tryptophan biosynthesis might confer the ethanol stress tolerance to yeast cells. Indeed, the strains overexpressing tryptophan biosynthesis genes showed a stress tolerance to 5% ethanol. Moreover, the addition of tryptophan to the culture medium and overexpression of tryptophan permease gene conferred ethanol stress tolerance to yeast cells. These results indicate that overexpression of the genes for trypophan biosynthesis increases the ethanol stress tolerance. Tryptophan supplementation to culture and overexpression of the tryptophan permease gene are also effective for the increase in ethanol stress tolerance. Our methodology for the selection of target genes for constructing ethanol stress tolerant strains, based on the data of DNA microarray analysis and phenotypes of knockout mutants, was validated.     

Rat <Emphasis Type="Italic">wct</Emphasis> mutation prevents differentiation of maturation-stage ameloblasts resulting in hypo-mineralization in incisor teeth

A recent study provided genetic and morphological evidence that rat autosomal-recessive mutation, whitish chalk-like teeth (wct), induced tooth enamel defects resembling those of human amelogenesis imperfecta (AI). The wct locus maps to a specific interval of rat chromosome 14 corresponding to human chromosome 4q21 where the ameloblastin and enamelin genes exist, although these genes are not included in the wct locus. The effect of the wct gene mutation on the enamel matrix synthesis and calcification remains to be elucidated. This study clarifies how the wct gene mutation influences the synthesis of enamel matrix and its calcification by immunocytochemistry for amelogenin, ameloblastin and enamelin, and by electron probe micro-analysis (EPMA). The immunoreactivity for enamel proteins such as amelogenin, ameloblastin, and enamelin in the ameloblasts in the homozygous teeth was the same as that in the heterozygous teeth from secretory to transitional stages, although the homozygous ameloblasts became detached from the enamel matrix in the transitional stage. The flattened ameloblasts in the maturation stage of the homozygous samples contained enamel proteins in their cytoplasm. Thus, the wct mutation was found to prevent the morphological transition of ameloblasts from secretory to maturation stages without disturbing the synthesis of enamel matrix proteins, resulting in the hypo-mineralization of incisor enamel and cyst formation between the enamel organ and matrix. This mutation also prevents the transfer of iron into the enamel.     

The Spemann organizer meets the anterior‐most neuroectoderm at the equator of early gastrulae in amphibian species

The dorsal blastopore lip (known as the Spemann organizer) is important for making the body plan in amphibian gastrulation. The organizer is believed to involute inward and migrate animally to make physical contact with the prospective head neuroectoderm at the blastocoel roof of mid‐ to late‐gastrula. However, we found that this physical contact was already established at the equatorial region of very early gastrula in a wide variety of amphibian species. Here we propose a unified model of amphibian gastrulation movement. In the model, the organizer is present at the blastocoel roof of blastulae, moves vegetally to locate at the region that lies from the blastocoel floor to the dorsal lip at the onset of gastrulation. The organizer located at the blastocoel floor contributes to the anterior axial mesoderm including the prechordal plate, and the organizer at the dorsal lip ends up as the posterior axial mesoderm. During the early step of gastrulation, the anterior organizer moves to establish the physical contact with the prospective neuroectoderm through the “subduction and zippering” movements. Subduction makes a trench between the anterior organizer and the prospective neuroectoderm, and the tissues face each other via the trench. Zippering movement, with forming Brachet's cleft, gradually closes the gap to establish the contact between them. The contact is completed at the equator of early gastrulae and it continues throughout the gastrulation. After the contact is established, the dorsal axis is formed posteriorly, but not anteriorly. The model also implies the possibility of constructing a common model of gastrulation among chordate species.     

Long-chain Acylcarnitines Reduce Lung Function by Inhibiting Pulmonary Surfactant

The role of mitochondrial energy metabolism in maintaining lung function is not understood. We previously observed reduced lung function in mice lacking the fatty acid oxidation enzyme long-chain acyl-CoA dehydrogenase (LCAD). Here, we demonstrate that long-chain acylcarnitines, a class of lipids secreted by mitochondria when metabolism is inhibited, accumulate at the air-fluid interface in LCAD^−/− lungs. Acylcarnitine accumulation is exacerbated by stress such as influenza infection or by dietary supplementation with l-carnitine. Long-chain acylcarnitines co-localize with pulmonary surfactant, a unique film of phospholipids and proteins that reduces surface tension and prevents alveolar collapse during breathing. In vitro, the long-chain species palmitoylcarnitine directly inhibits the surface adsorption of pulmonary surfactant as well as its ability to reduce surface tension. Treatment of LCAD^−/− mice with mildronate, a drug that inhibits carnitine synthesis, eliminates acylcarnitines and improves lung function. Finally, acylcarnitines are detectable in normal human lavage fluid. Thus, long-chain acylcarnitines may represent a risk factor for lung injury in humans with dysfunctional fatty acid oxidation.     

A deletion in a cis element of Foxe3 causes cataracts and microphthalmia in rct mice

The Rinshoken cataract (rct) mutation, which causes congenital cataracts, is a recessive mutation found in SJL/J mice. All mutants present with opacity in the lens by 2?months of age. The rct locus was mapped to a 1.6-Mb region in Chr 4 that contains the Foxe3 gene. This gene is responsible for cataracts in humans and mice, and it plays a crucial role in the development of the lens. Furthermore, mutation of Foxe3 causes various ocular defects. We sequenced the genomic region of Foxe3, including the coding exons and UTRs; however, no mutations were discovered in these regions. Because there were no differences in Foxe3 sequences between the rct/rct and wild-type mice, we inferred that a mutation was located in the regulatory regions of the Foxe3 gene. To test this possibility, we sequenced a 5' noncoding region that is highly conserved among vertebrates and is predicted to be the major enhancer of Foxe3. This analysis revealed a deletion of 22-bp located approximately 3.2-kb upstream of the start codon of Foxe3 in rct mice. Moreover, we demonstrated by RT-PCR and in situ hybridization that the rct mutant has reduced expression of Foxe3 in the lens during development. We therefore suggest that cataracts in rct mice are caused by reduced Foxe3 expression in the lens and that this decreased expression is a result of a deletion in a cis-acting regulatory element.