STEROL DISTRIBUTION IN THE GENUS HETEROCAPSA (PYRRHOPHYTA)1

The sterol composition of seven strains of marine peridinioid dinoflagellates comprising the four known species of Heterocapsa Stein was examined by gas chromatography-mass spectrometry to determine the utility of these compounds in systematics. Cholest-5-en-3β-ol (cholesterol), 24-methyl-cholest-5-en-3β-ol (24-methylcholesterol), 4α,24(S)-dimethyl-5α-cholestan-3β-ol (4,24-dimethylcholestanol), 4α,23,24(R)-trimethyl-5α-cholest-22-en-3β-ol (dinosterol), 4α,23ξ,24ξ-trimethyl-5α-cholestan-3β-ol (dihydrodinosterol), and an unknown sterol were detected. Sterol composition does not vary significantly from species to species within the genus Heterocapsa and thus cannot be used for species differentiation. Sterols may, however, have value in defining the properties of dinoflagellate taxa above the family level. Over the course of the growth curve for Heterocapsa niei (Loeblich) Morrill & Loeblich 4,24-dimethylcholestanol and dinosterol covaried, suggesting that 4,24-dimethylcholestanol is converted into dinosterol by a previously proposed bioalkylation scheme.     

Visceral adipose tissue modulates mammalian longevity

Caloric restriction (CR) can delay many age-related diseases and extend lifespan, while an increase in adiposity is associated with enhanced disease risk and accelerated aging. Among the various fat depots, the accrual of visceral fat (VF) is a common feature of aging, and has been shown to be the most detrimental on metabolic syndrome of aging in humans. We have previously demonstrated that surgical removal of VF in rats improves insulin action; thus, we set out to determine if VF removal affects longevity. We prospectively studied lifespan in three groups of rats: ad libitum-fed (AL-fed), CR (Fed 60% of AL) and a group of AL-fed rats with selective removal of VF at 5 months of age (VF-removed rats). We demonstrate that compared to AL-fed rats, VF-removed rats had a significant increase in mean (p < 0.001) and maximum lifespan (p < 0.04) and significant reduction in the incidence of severe renal disease (p < 0.01). CR rats demonstrated the greatest mean and maximum lifespan (p < 0.001) and the lowest rate of death as compared to AL-fed rats (0.13). Taken together, these observations provide the most direct evidence to date that a reduction in fat mass, specifically VF, may be one of the possible underlying mechanisms of the anti-aging effect of CR.     

mGluR1/5-dependent long-term depression requires the regulated ectodomain cleavage of neuronal pentraxin NPR by TACE

Matrix metalloproteases (MMPs) play a role in remodeling the extracellular matrix during brain development and have been implicated in synaptic plasticity. Here, we report that a member of the neuronal pentraxin (NP) family, neuronal pentraxin receptor (NPR), undergoes regulated cleavage by the MMP tumor necrosis factor-alpha converting enzyme (TACE). NPR is enriched at excitatory synapses where it associates with AMPA-type glutamate receptors (AMPAR) and enhances synaptogenesis. However, in response to activation of group 1 mGluRs (mGluR1/5), TACE cleaves NPR and releases the pentraxin domain from its N-terminal transmembrane domain. Cleaved NPR rapidly accumulates in endosomes where it colocalizes with AMPAR. This process is necessary for mGluR1/5-dependent LTD in hippocampal and cerebellar synapses. These observations suggest that cleaved NPR functions to "capture" AMPAR for endocytosis and reveal a bifunctional role of NPs in both synapse strengthening and weakening.     

Humanin: A Novel Central Regulator of Peripheral Insulin Action

Background

Decline in insulin action is a metabolic feature of aging and is involved in the development of age-related diseases including Type 2 Diabetes Mellitus (T2DM) and Alzheimer''s disease (AD). A novel mitochondria-associated peptide, Humanin (HN), has a neuroprotective role against AD-related neurotoxicity. Considering the association between insulin resistance and AD, we investigated if HN influences insulin sensitivity.

Methods and Findings

Using state of the art clamp technology, we examined the role of central and peripheral HN on insulin action. Continuous infusion of HN intra-cerebro-ventricularly significantly improved overall insulin sensitivity. The central effects of HN on insulin action were associated with activation of hypothalamic STAT-3 signaling; effects that were negated by co-inhibition of hypothalamic STAT-3. Peripheral intravenous infusions of novel and potent HN derivatives reproduced the insulin-sensitizing effects of central HN. Inhibition of hypothalamic STAT-3 completely negated the effects of IV HN analog on liver, suggesting that the hepatic actions of HN are centrally mediated. This is consistent with the lack of a direct effect of HN on primary hepatocytes. Furthermore, single treatment with a highly-potent HN analog significantly lowered blood glucose in Zucker diabetic fatty rats. Based upon the link of HN with two age-related diseases, we examined if there were age associated changes in HN levels. Indeed, the amount of detectable HN in hypothalamus, skeletal muscle, and cortex was decreased with age in rodents, and circulating levels of HN were decreased with age in humans and mice.

Conclusions

We conclude that the decline in HN with age could play a role in the pathogenesis of age-related diseases including AD and T2DM. HN represents a novel link between T2DM and neurodegeneration and along with its analogues offers a potential therapeutic tool to improve insulin action and treat T2DM.     

The Role of Jasmonates in Floral Nectar Secretion

Plants produce nectar in their flowers as a reward for their pollinators and most of our crops depend on insect pollination, but little is known on the physiological control of nectar secretion. Jasmonates are well-known for their effects on senescence, the development and opening of flowers and on plant defences such as extrafloral nectar. Their role in floral nectar secretion has, however, not been explored so far. We investigated whether jasmonates have an influence on floral nectar secretion in oil-seed rape, Brassica napus. The floral tissues of this plant produced jasmonic acid (JA) endogenously, and JA concentrations peaked shortly before nectar secretion was highest. Exogenous application of JA to flowers induced nectar secretion, which was suppressed by treatment with phenidone, an inhibitor of JA synthesis. This effect could be reversed by additional application of JA. Jasmonoyl-isoleucine and its structural mimic coronalon also increased nectar secretion. Herbivory or addition of JA to the leaves did not have an effect on floral nectar secretion, demonstrating a functional separation of systemic defence signalling from reproductive nectar secretion. Jasmonates, which have been intensively studied in the context of herbivore defences and flower development, have a profound effect on floral nectar secretion and, thus, pollination efficiency in B. napus. Our results link floral nectar secretion to jasmonate signalling and thereby integrate the floral nectar secretion into the complex network of oxylipid-mediated developmental processes of plants.     

市售长叶松油和锡兰肉桂油对登革热媒蚊埃及伊蚊的灭幼效果(英文)

松油和桂皮油由于具有芳香性气味, 因而成为良好的成虫驱避剂, 但是关于它们对蚊虫的杀幼虫作用研究不多。为揭示市售的长叶松Pinus longifolia油和锡兰肉桂Cinnamomum zeylanicum油对来源于印度德里的埃及伊蚊Aedes aegypti 4龄幼虫的毒杀潜力, 我们进行了室内研究, 以幼虫死亡率及行为改变和形态改变等指标评估其杀幼虫潜力。结果表明： 两种油对埃及伊蚊4龄幼虫均具有毒杀作用, 且松油的灭幼效果优于桂皮油。松油的LC₅₀和LC₇₀ 值分别为0.33093 mg/L 和0.54476 mg/L, 而桂皮油的LC₅₀和LC₇₀ 值分别为0.63159 mg/L和0.77736。进一步观察发现, LC₉₀剂量下桂皮油的杀幼虫潜力强于松油, 其LC₉₀为1.11879 mg/L, 而松油的LC₉₀为 1.04915 mg/L。在处理的幼虫中观察到行为改变, 如兴奋、 坐立不安、 颤抖、 痉挛然后瘫痪, 说明这两种油可能对其神经肌肉系统产生了影响。显微观察处理幼虫的形态改变发现, 与对照相比, 大多数器官的外观正常, 只是肛鳃略为内收缩而引起结构畸形, 提示肛腮可能是这两种油的作用位点, 腮的功能异常引起了幼虫死亡。这两种油品可开发用作防治蚊虫的新型杀幼虫药剂。