Medaka fish exhibits longevity gender gap,a natural drop in estrogen and telomere shortening during aging: a unique model for studying sex-dependent longevity

Introduction

Females having a longer telomere and lifespan than males have been documented in many animals. Such linkage however has never been reported in fish. Progressive shortening of telomere length is an important aging mechanism. Mounting in vitro evidence has shown that telomere shortening beyond a critical length triggered replicative senescence or cell death. Estrogen has been postulated as a key factor contributing to maintenance of telomere and sex-dependent longevity in animals. This postulation remains unproven due to the lack of a suitable animal system for testing. Here, we introduce a teleost model, the Japanese medaka Oryzias latipes, which shows promise for research into the molecular mechanism(s) controlling sex difference in aging.

Results

Using the medaka, we demonstrate for the first time in teleost that (i) sex differences (female?>?male) in telomere length and longevity also exist in fish, and (ii) a natural, ‘menopause’-like decline of plasma estrogen was evident in females during aging. Estrogen levels significantly correlated with telomerase activity as well as telomere length in female organs (not in males), suggesting estrogen could modulate telomere length via telomerase activation in a sex -specific manner. A hypothetical in vivo ‘critical’ terminal restriction fragment (TRF, representing telomere) length of approximately 4 kb was deduced in medaka liver for prediction of organismal mortality, which is highly comparable with that for human cells. An age conversion model was also established to enable age translation between medaka (in months) and human (in years). These novel tools are useful for future research on comparative biology of aging using medaka.

Conclusion

The striking similarity in estrogen profile between aging female O. latipes and women enables studying the influence of “postmenopausal” decline of estrogen on telomere and longevity without the need of invasive ovariectomy. Medaka fish is advantageous for studying the direct effect of increased estrogen on telomere length and longevity without the breast cancer complications reported in rodents. The findings strongly support the notion that O. latipes is a unique non-mammalian model for validation of estrogenic influence on telomere and longevity in vertebrates. This laboratory model fish is of potential significance for deciphering the ostensibly conserved mechanism(s) of sex-associated longevity in vertebrates.

     

Use of essential oil as botanical-pesticide against post harvest spoilage in Malus pumilo fruit

During antifungal screening of the essentialoils of some angiospermic plants, oil ofCymbopogon flexuosus showed potentbioactivity against dominant post harvestfungal pathogens. The minimum bioactiveconcentrations with fungicidal action of theoil was found to be 0.2 µl ml^–1 for Alternaria alternata, 0.4 µlml^–1 for Aspergillus flavus, A.fumigatus, A. niger, A. parasiticus,Cladosporium cladosporioides, Colletotrichumcapsici, C. falcatum, Curvularia lunata,Fusarium cerealis, F. culmorum, F. oxysporum,F. udum, Gloeosporium fructigenum, Penicilliumexpansum, P. italicum, P. implicatum, P. digitatum,P. minio-luteum, P. variable,and 0.5 µl ml^–1 forBotrytis cinerea, Helminthosporium oryzae, H.maydis, Phoma violacea, Rhizopus nigricans.The oil exhibited potency against heavy doses(30 mycelial disc, each of 5 mm in diameter) ofinoculum at 1.0 µl ml^–1 concentrations.The bioactivity of the oil was thermostable upto 100°C and lasted up to 48 months.The oil preparation did not exhibit anyphytotoxic effect on the fruit skins ofMalus pumilo up to 50 µlml^–1 concentrations. In vivo trials of theoil as a fungicidal spray on Malus pumilofor checking the rotting of fruits, it showedthat 20 µl ml^–1 concentration controls100% infection by pre-inoculation treatment,while in post-inoculation treatment, 30 µlml^–1 concentration of fungicidal spraywas required for the 100% control of rotting.The fungicidal spray was found to be costeffective (INR 15/l), has long shelf life (48month) and was devoid of any adverse effects.Therefore, it can be used as a potential sourceof sustainable eco-friendly botanicalpesticide, after successfulcompletion of wide range trials.     

Effect of different levels of gypsum application on soil characteristics and growth and yield of rice (Oryza sativa L.)

Summary A field experiment was conducted to compare the efficacy of application of different fractions of gypsum requirement (0, 20, 40, 60, 80 and 100%) for reclaiming alkali lands for rice cultivation. The experiment was initiated in the year 1971 and the effect of treatments was observed for three consecutive years (upto 1973) in terms of rice growth and yield and also the chemical characteristics of the soil. Economics of rice production was also worked out for different treatments.Results obtained revealed that a fairly good crop of rice with a small profit margin could be raised in the first year itself, by applying 20% of the gypsum requirement. Higher levels of gypsum proved economical only during subsequent years. Application of gypsum beyond 80% of the requirement was of no avail. Soil pH declined in all the treatments with its magnitude dilating with increased gypsum application. Electrical conductivity was also brought down with rice cultivation, irrespective of the quantum of gypsum.     

A Biochemical Study of Spore Germination in the Blue-green Alga Anabaena doliolum

The spores of Anabaena doliolum formed in light (light spores)and after transfer to darkness (dark spores) are biochemicallydifferent in that the light spores contain chlorophyll a andphycocyanin, while dark spores seem to lack them. The apparentbiosyntheses accompanying dark-spore germination seem to proceedin the following order: RNA, chlorophyll a, phycocyanin andDNA. Results of chloramphenicol treatment indicate that proteinsynthesis precedes RNA synthesis. The biosynthetic events followingRNA synthesis show a requirement for light.     

Moderate O3/O2 therapy enhances enzymatic and non-enzymatic antioxidant in brain and cochlear that protects noise-induced hearing loss

Mitochondrial damage and oxidative stress are known to contribute to the pathogenesis of noise-induced hearing loss (NIHL). In this study, we examined the protective effect of O₂/O₃ mixture (ozone/oxygen) therapy against mitochondrial induced damage and oxidative stress by noise exposure in rat brain and cochlear. For this purpose, rats were divided into four groups: 1 – control group; 2 – noise-exposed group (100?dB); 3 – noise?+?O₂/O₃, and 4 – O₂/O₃ (30 µg/ml). After 14 d, animals were anesthetised. Rat brain and cochlear tissue were removed for evaluation of the histopathological damages, oxidative stress, and mitochondrial dysfunction in both tissues. Our findings indicated that noise caused pathological damage, oxidative stress, and mitochondrial dysfunction in rat brain and cochlear. Also, daily administration of an O₂/O₃ therapy (30 µg/ml intravenous) efficiently increased enzymatic and non-enzymatic antioxidant in brain and cochlear that this action led to inhibition of pathological damages, oxidative stress, reactive oxygen species formation, mitochondrial membrane potential (MMP) collapse, mitochondrial swelling, and cytochrome c release resulting from noise. These findings suggest that the moderate O₂/O₃ therapy enhances the capacity of enzymatic and non-enzymatic antioxidant in brain and cochlear that protects against NIHL.     

Sterol transport by the human breast cancer resistance protein (ABCG2) expressed in Lactococcus lactis

The human breast cancer resistance protein (BCRP, also know as ABCG2, MXR, or ABCP) is one of the more recently discovered ATP-binding cassette (ABC) transporters that confer resistance on cancer cells by mediating multidrug efflux. In the present study, we have obtained functional expression of human BCRP in the Gram-positive bacterium Lactococcus lactis. BCRP expression conferred multidrug resistance on the lactococcal cells, which was based on ATP-dependent drug extrusion. BCRP-mediated ATPase and drug transport activities were inhibited by the BCRP-specific modulator fumitremorgin C. To our knowledge these data represent the first example of the functional expression of a mammalian ABC half-transporter in bacteria. Although members of the ABCG subfamily (such as ABCG1 and ABCG5/8) have been implicated in the transport of sterols, such a role has not yet been established for BCRP. Interestingly, the BCRP-associated ATPase activity in L. lactis was significantly stimulated by (i) sterols including cholesterol and estradiol, (ii) natural steroids such as progesterone and testosterone, and (iii) the anti-estrogen anticancer drug tamoxifen. In addition, BCRP mediated the efflux of [3H]estradiol from lactococcal cells. Our findings suggest that BCRP may play a role in the transport of sterols in human, in addition to its ability to transport multiple drugs and toxins.