Effect of Hillslope Gradient on Vegetation Recovery on Abandoned Land of Shifting Cultivation in Hainan Island, South China

In the present study, we investigated the effect of hillslope gradient on vegetation recovery on abandoned land of shifting cultivation In Hainan Island, south China, by measuring community composition and structure of 25-year-old secondary forest fallows along a hillslope gradient （up-, middle-, and down-slope position）. A total of 49 733 free-standing woody plant stems higher than 10 cm and belonging to 170 species, 112 genera, and 57 families was found in the three l-hm2 investigation plots. Stem density was highest in the down-slope stand and lowest in the up-slope stand. Species richness and the Shannon-Wiener Index were both highest in the middle-slope stand, and lower In the down-slope and up-slope stands. The recovery forest fallows on different hiUslope positions were all dominated by a few species. The five most abundant species accounted for 70.1%, 58.8%, and 72.9% of total stem densities in stands in the up-, middle-, and down-slope positions, respectively. The five species with the greatest basal areas accounted for 74.5%, 84.3%, and 74.7% of total stem basal area for the up-, middle-, and down-slope positions, respectively. The number of low-density species （stem abundance less than five） Increased from the up-slope position downward. Of the nine local common species among three different functional groups, the short-lived pioneer species dominated the up-slope position, but long-lived pioneer species dominated the middle- and down-slope positions. The climax species of primary tropical lowland rain forest was found in the downslope position. Both the mean diameter at breast height （DBH） and mean height of the trees Increased with decreasing hillslope gradient. The stem density and basal area in different size classes were significantly different in stands In different slope positions. Our results indicated that the rate of secondary succession varies, even over small spatial scales caused by the hlllslope gradient, in early vegetation recovery.     

Bird community patterns in response to the island features of urban woodlots in eastern China

Many studies have demonstrated the changes in the spatial patterns of plant and animal communities with respect to habitat fragmentation. Insular communities tend to exhibit some special patterns in connection with the characteristics of island habitats. In this paper, the relationships between richness, assemblage, and abundance of bird communities with respect to island features were analyzed in 20 urban woodlots in Hangzhou, China. Field investigations of bird communities, using the line transect method, were conducted from January to December, 1997. Each woodlot was surveyed 16 times during the year. Results indicated that bird richness was higher, per unit area, in the smaller woodlots than the larger ones, and overall bird density decreased with the increase in the size of woodlot. However, the evenness of species abundance increased with the area, and small woodlots were usually dominated by higher density species and large woodlots by medium density species. Most species occurring in the small woodlots also occurred in larger woodlots. Also, bird communities among urban woodlots showed a nestedness pattern in assemblage. These patterns implied that the main impacts of woodland habitat fragmentation are: (1) species are constricted and thus species number will increase at a given sample size; (2) as surface area decreases, the proportion of forest edge species as to interior species will increase; (3) community abundance will therefore increase per unit area but most individuals will be from a few dominant species; and (4) overall species diversity will decrease at a habitat level as well as at a region level. These patterns of community in response to the island features were therefore summarized as “island effects in community”. The underlying processes of such observations were also examined in this paper. Woodlot area, edge ratio, isolation, and habitat nestedness were considered as the important factors forming the island effects in community. High heterogeneity between habitats usually contributed most to the maintenance of regional biodiversity, especially in urban woodlots. __________ Translated from Acta Ecologica Sinica, 2005, 25(4): 657–663 [译自: 生态学报, 2005, 25(4): 657–663]     

巨龙竹生殖器官形态结构及雌、雄配子体的发育

通过石蜡切片的方法对巨龙竹生殖器官结构、大小孢子的发生和雌、雄配子体的发育过程进行了观察研究。 巨龙竹为一心皮组成的单室单子房,子房内具有一个胚珠,倒生、双珠被、厚珠心。大孢子母细胞减数分裂形成线形排列的4个大孢子,合点端大孢子具功能。胚囊的发育为蓼型,具多个反足细胞。巨龙竹的花药壁由4层结构组成,包括表皮、药室内壁、中层、绒毡层;花药壁发育为单子叶型,绒毡层为腺质型。小孢子母细胞减数分裂中的胞质分裂为连续型,四分孢子为四面体型;成熟花粉粒为2细胞型,具1个萌发孔。小穗发育雌雄异熟,雌蕊的发育早于雄蕊的发育。     

禽流感病毒血凝素蛋白的结构、功能与表达

血凝素蛋白（HA）既是一种重要吸附蛋白,介导禽流感病毒吸附和穿入宿主细胞而发挥致病作用,也是一种良好的保护性抗原,对宿主抵抗禽流感起到了决定性保护作用。研究HA蛋白对揭示禽流感病毒的致病机理和免疫防治禽流感均具有重要意义。本文重点概述了HA蛋白的结构、功能和蛋白表达方面的研究进展,并对HA蛋白在禽流感疫苗中的应用进行了探讨。     

Two-step fluorescence screening of CD21-binding peptides with one-bead one-compound library and investigation of binding properties of N-(2-hydroxypropyl)methacrylamide copolymer-peptide conjugates

Using the one-bead one-compound (OBOC) combinatorial method, four heptapeptide ligands of CD21 receptor, a cell surface marker of malignant B cell lymphoma, were identified with an innovative two-step fluorescence screening method to overcome the limitation caused by autofluorescence of TentaGel resin. The binding affinities of selected peptides, YILIHRN (B1), PTLDPLP (B2), and LVLLTRE (B3), were in the micromolar region as determined by a fluorescence quenching assay. Peptide B1 was conjugated to N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer via spacers of different lengths, composed of one to four repeats of the 8-amino-3,6-dioxaoctanoic acid (A) group. The evaluation of the biorecognizability of HPMA copolymer-B1 conjugates by the CD21 receptor revealed that increasing the number of repeats of A in the spacer from one to three resulted in continuous improvements in the biorecognition by the CD21 receptor; the increase from three to four repeats showed no significant effect. This work showed the potential of the OBOC combinatorial approach to select peptide ligands as targeting moieties for CD21 specific polymeric drug carriers.     

Store-operated Ca2+ channel in renal microcirculation and glomeruli

Store-operated Ca2+ channel (SOC) is defined as a channel that opens in response to depletion of the internal Ca2+ stores. During the last decade, many investigators have made a great effort to identify and characterize SOC, and to evaluate its physiologic function and pathophysiologic relevance in a variety of cell lines, primary cultures, and native tissues. To date, accumulating evidence has demonstrated that SOC is an essential Ca2+ entry mechanism in vascular smooth-muscle cells of renal microvasculature and glomerular mesangial cells, both of which tightly control glomerular hemodynamics and filtration. Store-operated Ca2+, combined with other types of Ca2+ entry channels, constitutes a profile of Ca2+ changes in response to physiologic vasoconstrictors and, thereby, regulates renal microcirculation and mesangial function. In addition, SOC is associated with altered Ca2+ signaling occurring in diseased kidneys, such as diabetic nephropathy. Although the gating mechanism and molecular identity of SOC are still enigmatic and may be cell-type and tissue specific, data from several independent groups suggest that protein kinase C plays an important role in SOC activation and that certain isoforms of canonical transient receptor potential (TRPC) proteins are candidates of SOC in renal microvessels and mesangial cells.     

Global patterns of geographic range size in birds

Large-scale patterns of spatial variation in species geographic range size are central to many fundamental questions in macroecology and conservation biology. However, the global nature of these patterns has remained contentious, since previous studies have been geographically restricted and/or based on small taxonomic groups. Here, using a database on the breeding distributions of birds, we report the first (to our knowledge) global maps of variation in species range sizes for an entire taxonomic class. We show that range area does not follow a simple latitudinal pattern. Instead, the smallest range areas are attained on islands, in mountainous areas, and largely in the southern hemisphere. In contrast, bird species richness peaks around the equator, and towards higher latitudes. Despite these profoundly different latitudinal patterns, spatially explicit models reveal a weak tendency for areas with high species richness to house species with significantly smaller median range area. Taken together, these results show that for birds many spatial patterns in range size described in geographically restricted analyses do not reflect global rules. It remains to be discovered whether global patterns in geographic range size are best interpreted in terms of geographical variation in species assemblage packing, or in the rates of speciation, extinction, and dispersal that ultimately underlie biodiversity.     

Enhanced expression of LKB1 in breast cancer cells attenuates angiogenesis, invasion, and metastatic potential

LKB1 (also known as STK11) is a recently identified tumor suppressor gene whose mutation can lead to Peutz-Jeghers syndrome, which is characterized by gastrointestinal polyps and cancers of different organ systems. Approximately 30% of sporadic breast cancer samples express low levels of LKB1. This suggests that the LKB1 gene may be related to the tumorigenesis of breast cancer. We reintroduced LKB1 into MDA-MB-435 breast cancer cells that lack the LKB1 gene to investigate how overexpression of LKB1 affects tumor invasiveness and metastasis. Overexpression of the LKB1 protein in breast cancer cells resulted in significant inhibition of in vitro invasion. In vivo, LKB1 expression reduced tumor growth in the mammary fat pad, microvessel density, and lung metastasis. LKB1 overexpression was associated with down-regulation of matrix metalloproteinase-2, matrix metalloproteinase-9, vascular endothelial growth factor, and basic fibroblast growth factor mRNA and protein levels. Overexpression of the LKB1 protein in human breast cancer is significantly associated with a decrease in microvessel density. Our results indicate that LKB1 plays a negative regulatory role in human breast cancer, a finding that may lead to a new therapeutic strategy.     

URI1 suppresses irradiation-induced reactive oxygen species (ROS) by activating autophagy in hepatocellular carcinoma cells

Radiotherapy has been extensively applied in cancer treatment. However, this treatment is ineffective in Hepatocellular carcinoma (HCC) due to lack of radiosensitivity. Unconventional prefoldin RPB5 interactor 1 (URI1) exhibits characteristics similar to those oncoproteins, which promotes survival of cancer cells. As a consequence of the irradiation, the levels of endogenous reactive oxygen species (ROS) rise. In the current study, we analyzed the role of URI1 in the control of ROS levels in HepG2 cells. Upon URI1 overexpression, HepG2 cells significantly suppressed irradiation-induced ROS, which may help cells escape from oxidative toxicity. And our data demonstrated that overexpression of URI1 not only resulted in an increase of autophagic flux, but also resulted in an further increased capacity of autophagy to eliminate ROS. It indicated that URI1 suppressed irradiation-induced ROS through activating autophagy. Moreover, URI1 activated autophagy by promoting the activities of AMP-activated protein kinase (AMPK). Results showed that overexpression of URI1 increased the phosphorylation of AMPKα at the Thr172 residue and the activated-AMPK promoted the phosphorylation of forkhead box O3 (FOXO3) at the Ser253 residue, which significantly induced autophagy. Taken together, our findings provide a mechanism that URI1 suppresses irradiation-induced ROS by activating autophagy through AMPK/FOXO3 signaling pathway. These new molecular insights will provide an important contribution to our better understanding about irradiation insensitivity of HCC.     

Altered Regulation of CD200 Receptor in Monocyte-Derived Macrophages from Individuals with Parkinson’s Disease

Microglia are the representative myeloid cells in the brain, and their over-activation plays an important role in the pathogenesis of Parkinson’s disease (PD). Microglia activation is believed to be regulated by the CD200-CD200R signaling. As the peripheral counterpart of microglia, monocyte-derived macrophages (MDMs) share the same progenitor and antigen markers, and they have similar biological behaviors and mirror microglial function in the brain. Here, we studied CD200R expression and its regulation in MDMs from 32 PD cases, 27 age-matched old controls, and 28 young controls. We found that the basal CD200R expression is similar in MDMs from young control, old control and PD patients. However, the induction of CD200R expression in MDMs under various conditions is impaired in the old groups, especially in PD patients. There was a selective decrease in CD200R expression induced by co-culture with dying PC12 cells in MDMs from PD cases, as compared with MDMs from the age-matched controls. We also found that the inducible CD200R expression correlated inversely with the onset age of PD and to tumor necrosis factor-α (TNF-α) released from MDMs. These results suggest an intrinsic abnormality in the CD200-CD200R signaling in MDMs during aging and, especially, in PD. We speculate that in the PD brain, microglia might undergo abnormalities similar to MDMs.