[A two-step approach for modeling tree mortality in Larix olgensis plantation based on effects of thinning]. / 基于抚育间伐效应的长白落叶松人工林两阶段枯死模型.

Ten permanent plots of Larix olgensis plantation were established in 1972 and 1974 at Jiangshanjiao and Mengjiagang forest farms in Heilongjiang Province, respectively. The plots including 8 thinning plots and 2 control plots were measured annually. The effects of thinning on the probability of plot mortality and individual tree mortality were analyzed. Based on the binary logistic regression, two-step models of the probability of mortality were developed. The approach consisted of estimating the probability of mortality after thinning on a sample plot (1) and the mortality of individual tree within mortality plots (2). The generalized estimating equations (GEE) method was adopted to estimate the parameters of models. An optimal cutpoint was determined for each model by plotting the sensitivity curve and the specificity curve and choosing the cutpoint at which the specificity and sensitivity curves cross. The results showed that four models (models 1-4) were developed based on the data of plots which was divided into 4 groups by thinning times, respectively. The significant explicatory variables of model 1 were site index, the logarithm of stand age, thinning age and thinning intensity. Principal component analysis was used to develop models 2-4. The primal variables of the principal components were stand age, tree numbers per hectare, mean square diameter at breast height and thinning factors. This showed that thinning significantly affected the probability of plot mortality. The effect of thinning was not significant for the pro-bability of individual tree mortality. The significant variables of the individual tree mortality model were planting density, age, the inverse of diameter at breast height and the basal area of all trees larger than the subject tree. Hosmer and Lemeshow goodness of fit tests were not significant for the mortality models of plots and individual trees (P＞0.05). The areas under the receiver operating characteristic curve (AUC) of the models were all greater than 0.91, the accuracies were all above 80%, suggesting the fitting results of the models performed very well.

Prevention of UV-induced skin damages by 11,14,17-eicosatrienoic acid in hairless mice in vivo.

Polyunsaturated fatty acids (PUFAs) are known to play important roles in various physiological and pathological processes. Recent studies have shown that some omega-3 (omega-3) PUFAs, such as eicosapentaenoic acid (EPA) and dodecahexaenoic acid (DHA), have protective effects on acute and chronic UV-induced changes. However, the effects of other omega-3 PUFAs including 11,14,17-eicosatrienoic acid (20:3) (ETA) on UV-induced skin damages are poorly understood. In this study, we investigated the cutaneous photoprotective effects of ETA in hairless mice in vivo. Female HR-1 hairless mice were topically treated with vehicle (ethanol:polyethylene glycol=30:70) only, 0.1% ETA, or 1% ETA once a day for 3 successive days after one time UV irradiation (200 mJ/cm(2)) on dorsal skins. Skin biopsy was carried out on the fourth day (72 hr after UV irradiation). We found that topical treatment with ETA attenuated UV-induced epidermal and dermal thickness and infiltration of inflammatory cells, and impairment of skin barrier function. In addition, ETA suppressed the expression of IL-1beta, COX-2, and MMP-13 induced by UV irradiation. Our results show that the topical application of ETA protects against UV-induced skin damage in hairless mice and suggest that ETA can be a potential agent for preventing and/or treating UV-induced inflammation and photoaging.

Skin aging and photoaging alter fatty acids composition, including 11,14,17-eicosatrienoic acid, in the epidermis of human skin.

We investigated the alterations of major fatty acid components in epidermis by natural aging and photoaging processes, and by acute ultraviolet (UV) irradiation in human skin. Interestingly, we found that 11,14,17-eicosatrienoic acid (ETA), which is one of the omega-3 polyunsaturated acids, was significantly increased in photoaged human epidermis in vivo and also in the acutely UV-irradiated human skin in vivo, while it was significantly decreased in intrinsically aged human epidermis. The increased ETA content in the epidermis of photoaged human skin and acute UV-irradiated human skin is associated with enhanced expression of human elongase 1 and calcium-independent phosphodiesterase A(2). We demonstrated that ETA inhibited matrix metalloproteinase (MMP)-1 expression after UV-irradiation, and that inhibition of ETA synthesis using EPTC and NA-TCA, which are elongase inhibitors, increased MMP-1 expression. Therefore, our results suggest that the UV increases the ETA levels, which may have a photoprotective effect in the human skin.

UV decreases the synthesis of free fatty acids and triglycerides in the epidermis of human skin in vivo, contributing to development of skin photoaging.

BACKGROUND: Although fatty acids are known to be important in various skin functions, their roles on photoaging in human skin are poorly understood. OBJECTIVE: We investigated the alteration of lipid metabolism in the epidermis by photoaging and acute UV irradiation in human skin. METHODS: UV irradiated young volunteers (21-33 years, n=6) and elderly volunteers (70-75 years, n=7) skin samples were obtained by punch biopsy. Then the epidermis was separated from dermis and lipid metabolism was investigated. RESULTS: We observed that the amounts of free fatty acids (FFA) and triglycerides (TG) in the epidermis of photoaged or acutely UV irradiated human skin were significantly decreased. The expressions of genes related to lipid synthesis, including acetyl-CoA carboxylase (ACC), fatty acid synthase (FAS), stearoyl-CoA desaturase (SCD), sterol regulatory element binding proteins (SREBPs), and peroxisome proliferator-activated receptors (PPARgamma) were also markedly decreased. To elucidate the significance of these changes of epidermal lipids in human skin, we investigated the effects of TG or various inhibitors for the enzymes involved in TG synthesis on the expression of matrix metalloproteinase-1 (MMP-1) in cultured human epidermal keratinocytes. We demonstrated that triolein (TG) reduced basal and UV-induced MMP-1 mRNA expression. In addition, each inhibitor for various lipid synthesis enzymes, such as TOFA (ACC inhibitor), cerulenin (FAS inhibitor) and trans-10, cis-12-CLA (SCD inhibitor), increased the MMP-1 expression significantly in a dose-dependent manner. We also demonstrated that triolein could inhibit cerulenin-induced MMP-1 expression. Furthermore, topical application of triolein (10%) significantly prevented UV-induced MMP-13, COX-2, and IL-1beta expression in hairless mice. CONCLUSION: Our results suggest that TG and FFA may play important roles in photoaging of human skin.

Cloning and characterization of a dextranase gene from Lipomyces starkeyi and its expression in Saccharomyces cerevisiae.

A dextranase-encoding cDNA from L. starkeyi KSM22 was isolated and characterized. The 2052 bp cDNA fragment (lsd1) harbouring the dextranase gene exhibited one open reading frame (ORF) composed of 1824 bp flanked by a 41 bp 5'-UTR and a 184 bp 3'-UTR, including a 27 bp poly(A) tail. The lsd1 gene contains no introns. The open reading frame encodes a 608 amino acid polypeptide (LSD1) with a 67.6 kDa predicted molecular mass. There was a 77% deduced amino acid sequence identity between the LSD1 dextranase and the dextranase from Penicillium minioluteum. The primary structure of LSD1 dextranase exhibits distant similarity with the enzymes of the glycosyl hydrolase family 49 that comprises Penicillium dextranase. The optimum pH of LSD1 was 6.0 and the optimum temperature was 37 degrees C. LSD1 dextranase activity was substantially abolished by exposure to 1 mM Hg2+, Ag3+ and Mn2+. LSD1 exhibited high hydrolysing activity towards dextran (100%), soluble starch (22%) and mutan (8%).