Kenshi Suzuki

A mutation in succinate dehydrogenase cytochrome b causes oxidative stress and ageing in nematodes

Much attention has focused on the aetiology of oxidative damagein cellular and organismal ageing. Especially toxic arethe reactive oxygen byproducts of respiration and other biological processes. A mev-1 (kn1 ) mutant of Caenorhabditis elegans has been found to be hypersensitive to raised oxygen concentrations,. Unlike the wild type, its lifespan decreases dramatically as oxygen concentrations are increased from 1 to 60% (ref. 7). Strains bearing this mutation accumulate markers of ageing (such as fluorescent materials and protein carbonyls) faster than the wild type,. We show here that mev-1 encodes a subunit of the enzyme succinate dehydrogenase cytochrome b , which is a component of complex II of the mitochondrial electron transport chain. We found that the ability of complex II to catalyse electron transport from succinate to ubiquinone is compromised in mev-1 animals. This may cause an indirect increase in superoxide levels, which in turn leads to oxygen hypersensitivity and premature ageing. Our results indicate that mev-1 governs the rate of ageing by modulating the cellular response to oxidative stress.

Differential age-change in the numbers of CD4+CD45RA+ DC4+CD29+ T cell subsets in human peripheral blood

Peripheral blood mononuclear cells were obtained from people ranging in age from newborn to 102 years old and analyzed by dual color flow cytometer in terms of number and percentage of various subsets of T cells, B cells and natural killer cells (CD3, 4, 5, 8, 11b, 19, 20, 21, 25, 29, 45RA and 56). Numbers of T cells (CD3+ or CD5+ cells) significantly declined at the 3rd decade as compared with those of younger people, stayed at a relatively constant level between the 3rd and the 7th decade and gradually declined thereafter. In T cell subsets, both CD4 and CD8 positive positive cells decreased with age, but a decrease was more pronounced in the latter, showing an age-related increase of CD4/CD8 ratio. The most interesting finding was a contrasting age-change in two subsets of CD4+ T cells; i.e. a subset of suppressor inducer T cells (CD4+CD45RA+ naive cells) decreased with age, while a subset of helper inducer T cells (CD4+CD29+ memory cells) increased with age. CD20+ B cells also decreased with age in a manner similar to that observed in T cells. Natural killer cells (CD56) showed an increase in numbers with age. The relationship between these changes in various subsets of peripheral blood leukocytes and the age-related decline in immune functions has been discussed.

A methyl viologen-sensitive mutant of the nematode Caenorhabditis elegans.

A methyl viologen (paraquat)-sensitive mutant, mev-1 (LG III), in Caenorhabditis elegans was about 4 times more sensitive to methyl viologen than the wild type. This mutant was also hypersensitive to oxygen. The brood size was about 1/4 that of the wild type. The average life span was determined to be 9.3 days as compared to 14.3 days for the wild type. The activity of superoxide dismutase (SOD), a scavenging enzyme for superoxide anion, was about half the wild-type level. We suggest that oxygen radicals may be involved in the normal aging mechanism in C. elegans.

Rapid accumulation of fluorescent material with aging in an oxygen-sensitive mutant mev-1 of Caenorhabditis elegans

Mutations in mev-1 of the nematode Caenorhabditis elegans render animals hypersensitive to high oxygen concentrations. They also reduce life span. To further understand the effects of mev-1 on aging, accumulation of fluorescent material resembling lipofuscin was measured by biochemical and histological analyses. Fluorescent material accumulated in both wild type and mev-1 animals with increasing age. The mev-1 mutant accumulated more fluorescent material at a greater rate than dose wild type. Furthermore, the accumulation rates depended on concentration of oxygen. Since this phenotype has been widely used as an aging marker, these results validate mev-1s use as a model to study aging.

INACTIVATION OF BACTERIOPHAGE LAMBDA BY NEAR–ULTRAVIOLET IRRADIATION IN THE PRESENCE OF CHLORPROMAZINE

Abstract Bacteriophage λvir was inactivated when it was irradiated with near‐UV light in the presence of chlorpromazine. DNA strand breakage in the treated phage was indicated by alkaline sucrose gradient centrifugation. The number of the breaks was increased with increasing fluence. Although the inactivation rate was enhanced with a decreasing salt concentration in the reaction mixture and under a nitrogen atmosphere, the number of the strand breaks was not altered in either case. Therefore, the DNA strand breakage is not a sole lethal damage in the treated phage. The addition of NaN3 repressed the inactivation and the reaction in a D2O medium enhanced the inactivation even if the reaction mixture was irradiated under anaerobic conditions. Under anaerobic conditions, the inactivation occurs presumably via a radical mechanism.

CHLORPROMAZINE PHOTOSENSITIZATION–II. FAILURE TO DETECT ANY EVIDENCE FOR INVOLVEMENT OF DNA DAMAGE IN THE PHOTODYNAMIC KILLING OF ESCHERICHIA COLI IN THE PRESENCE OF CHLORPROMAZINE

Abstract— When a suspension of Escherichia coli was irradiated with near‐UV light in the presence of chlorpromazine (at a concentration below a cytotoxic level), the cells were killed. Efficiency of the photodynamic killing was not influenced by the deficiency of the uvrA gene or the recA gene. Neither phenotypic reversion of E. coli Hs30R (arginine auxotroph) nor induction of lambda prophage in lysogenic bacteria was detected after this treatment.

The radiation-sensitive mutant RAD-8 of Caenorhabditis elegans is hypersensitive to the effects of oxygen on aging and development

A mutant of rad-8, originally isolated on the basis of its hypersensitivity to ultraviolet radiation, is also hypersensitive to oxygen and methyl viologen, a superoxide-anion generator. Oxygen also retarded development and reduced fecundity in a concentration-dependent fashion in rad-8 but not in wild type. In addition, the mean life span of rad-8 (but not wild type) was progressively shortened when animals incubated in increasing oxygen concentrations. This cross hypersensitivity to both UV radiation and free radicals provides further evidence that DNA damage may be important in the aging process.

Action spectra for inactivation of dry phage T1 after monochromatic (150-254 nm) synchrotron irradiation in the presence and absence of photoreactivation and dark repair.

Dry phage T1 was irradiated with monochromatic uv radiation (150-254 nm) in vacuo. The inactivation sensitivity was highest at 150 nm. On Escherichia coli Bs-1, the phage inactivation sensitivity was two and four times higher at 150 nm than at 254 and 230 nm, respectively. Action spectra for phage inactivation on both E. coli B and Bs-1 fit the absorption spectrum of phage DNA, except around 190 nm. The host-cell- reactivable fraction for vacuum-uv radiation (below 190 nm) was smaller than that with far-uv radiation. There was almost no photoreactivation at 150 nm, in contrast to a photoreactivation sector of about 0.3 at 254 nm.

SPECTROFLUOROMETRIC STUDY ON PHOTOCHEMICAL INTERACTION BETWEEN CHLORPROMAZINE AND NUCLEIC ACIDS

Abstract— Near‐UV irradiation of a mixture of chlorpromazine and single‐stranded nucleic acids produced a non‐dialyzable photoproduct which emitted characteristic fluorescence at around 520 nm. The same fluorescent species was also formed by the photoreaction with purine nucleotides but not with pyrimidine nucleotides. The highest photoreactivity was observed with GMP. Smaller amounts of the species were formed in a solution with a high salt concentration than in that with a low salt concentration. A higher rate was observed under anaerobic conditions than under aerobic conditions.

CHLORPROMAZINE PHOTOSENSITIZATION—I. EFFECT OF NEAR‐UV IRRADIATION ON BACTERIOPHAGES SENSITIZED WITH CHLORPROMAZINE

Abstract— Both DNA bacteriophage and RNA bacteriophage were inactivated when they were irradiated with near‐UV light (black light) in the presence of chlorpromazine. The far‐UV sensitive mutants of T4D, i.e. T4Dv, T4Dpx and T4Dy, were no more sensitive to near‐UV light plus chlorpromazine than the wild type. Electron microscopic observations showed that adsorption of T4D was greatly influenced by the treatment. The present results may indicate that the inactivation of T4D is due to the loss of adsorption caused by impairment in the tail or the tail fiber protein rather than the inactivation of DNA.