Latitudinal comparison of altitudinal changes in forest structure,leaf-type,and species richness in humid monsoon Asia

A new template for mountain vegetation zonation along latitudinal gradients is proposed for examining geographical pattern of various forest attributes in humid monsoon Asia. The contrasting temperature regime in tropical and temperate mountains, i.e., the former is a non-seasonal, temperature-sum controlled environment, and the latter is a seasonal, low temperature limiting environment, leads to different altitudinal patterns of tree height distribution and species richness. In the tropical mountains, both tree height and species richness decrease steeply, and the tree height often stepwise. The decline of tree height and species diversity in the temperate mountains is far less pronounced except near the forest limit. Both trends are explained by their temperature regime.     

The extracellular domain of p185(c-neu) induces density-dependent inhibition of cell growth in malignant mesothelioma cells and reduces growth of mesothelioma in vivo

EGFR is involved in the density-dependent inhibition of cell growth, while coexpression of EGFR with erbB2 can render normal cells transformed. In this study, we have examined the effect of a species of p185 that contains the transmembrane domain and the extracellular domain of p185(c-neu), on growth properties of a human malignant mesothelioma cell line that coexpresses EGFR and erbB2. The ectodomain form of p185(c-neu) enhanced density-dependent inhibition of cell growth and we found that p21 induction appeared to be responsible for this inhibitory effect. Previously, the extracellular domain species was shown to suppress the transforming abilities of EGFR and p185(c-neu/erbB2) in a dominant-negative manner. The ability of this subdomain to affect tumor growth is significant, as it reduced in vivo tumor growth. Unexpectedly, we found that the domain did not abrogate all of EGFR functions. We noted that EGFR-induced density-dependent inhibition of cell growth was retained. Tyrosine kinase inhibitors of EGFR did not cause density-dependent inhibition of cell growth of malignant mesothelioma cells. Therefore, simultaneously inhibiting the malignant phenotype and inducing density-dependent inhibition of cell growth in malignant mesothelioma cells by the extracellular domain of p185(c-neu) may represent an important therapeutic advance.     

TMPRSS13, a type II transmembrane serine protease, is inhibited by hepatocyte growth factor activator inhibitor type 1 and activates pro-hepatocyte growth factor

Type II transmembrane serine proteases (TTSPs) are structurally defined by the presence of a transmembrane domain located near the N-terminus and a C-terminal extracellular serine protease domain. The human TTSP family consists of 17 members. Some members of the family have pivotal functions in development and homeostasis, and are involved in tumorigenesis and viral infections. The activities of TTSPs are regulated by endogenous protease inhibitors. However, protease inhibitors of most TTSPs have not yet been identified. In this study, we investigated the inhibitory effect of hepatocyte growth factor activator inhibitor type 1 (HAI-1), a Kunitz-type serine protease inhibitor, on several members of the TTSP family. We found that the protease activity of a member, TMPRSS13, was inhibited by HAI-1. A detailed analysis revealed that a soluble form of HAI-1 with one Kunitz domain (NK1) more strongly inhibited TMPRSS13 than another soluble form of HAI-1 with two Kunitz domains (NK1LK2). In addition, an in vitro protein binding assay showed that NK1 formed complexes with TMPRSS13, but NK1LK2 did not. TMPRSS13 converted single-chain pro-hepatocyte growth factor (pro-HGF) to a two-chain form in vitro, and the pro-HGF converting activity of TMPRSS13 was inhibited by NK1. The two-chain form of HGF exhibited biological activity, assessed by phosphorylation of the HGF receptor (c-Met) and extracellular signal-regulated kinase, and scattered morphology in human hepatocellular carcinoma cell line HepG2. These results suggest that TMPRSS13 functions as an HGF-converting protease, the activity of which may be regulated by HAI-1.     

Secondary succession of plant communities in a subtropical mountainous region of SW China

Since 1985, originally forested mountainous areas of China have been allowed to return to their natural state after years of exploitation including agriculture, development, and logging. The reforms began earlier in less accessible locations, so that today the successional process is more advanced there. The vegetation in Luquan, Qiongzhusi, and Xishan near Kunming, central Yunnan, exhibits, in a limited area, a range of stages of plant succession that are widely encountered throughout the broader region, and thus affords a special opportunity for a comprehensive study. We analyzed the successional sequence of these various plant communities. They ranged from pioneer coniferous and/or pioneer deciduous broad-leaved stands to pre-mature semi-humid evergreen broad-leaved stands, through mixed coniferous and broad-leaved or mixed deciduous and evergreen broad-leaved stands. The succession proceeded from pioneer coniferous Pinus and Keteleeria, and deciduous Platycarya and Alnus, to late-successional evergreen broad-leaved Cyclobalanopsis and Castanopsis. Two regeneration types of woody species in either the early successional (15–50 years), the mid-successional (40–80 years), or the late-successional (80–180 years) stage were classified. Relatively high species diversity was found in the seral phase at the three study sites. The late-successional stage was commonest where human disturbance was least evident. Poor soil chemical properties under pioneer Pinus were seen as a limitation to plant growth, while the abundance of Alnus at the early stage led to an improved level of organic matter and nitrogen.     

Reverse pharmacology of orexin: from an orphan GPCR to integrative physiology

Orexins, which were initially identified as endogenous peptide ligands for two orphan G-protein coupled receptors (GPCRs), have been shown to have an important role in the regulation of energy homeostasis. Furthermore, the discovery of orexin deficiency in narcolepsy patients indicated that orexins are highly important factors for the sleep/wakefulness regulation. The efferent and afferent systems of orexin-producing neurons suggest interactions between these cells and arousal centers in the brainstem as well as important feeding centers in the hypothalamus. Electrophysiological studies have shown that orexin neurons are regulated by humoral factors, including leptin, glucose, and ghrelin as well as monoamines and acetylcholin. Thus, orexin neurons have functional interactions with hypothalamic feeding pathways and monoaminergic/cholinergic centers to provide a link between peripheral energy balance and the CNS mechanisms that coordinate sleep/wakefulness states and motivated behavior such as food seeking.     

Familial occurrence of a syndrome with mental retardation,nasal hypoplasia,peripheral dysostosis,and blue eyes in Japanese siblings

Summary Two Japanese siblings, a 2-year-old girl and a 7-month-old boy, had a syndrome of mental retardation, severe nasal hypoplasia, peripheral dysostosis, and blue eyes. The mother showed nasal hypoplasia of lesser degree and a mild form of peripheral dysostosis. This disorder bears a striking similarity to acrodysostosis, but in view of certain novel features its relationship to the disease is uncertain. The mode of inheritance could be either dominant with variable expressivity or autosomal recessive.     

Isotopic characteristics of typhonic rainwater: typhoons no. 13 (1993) and no. 6 (1996)

The stable isotope ratios of hydrogen and oxygen were measured for rainwater samples from Typhoon No. 13, which struck Japan on September 1993, and Typhoon No. 6, which passed in July 1996. Rainwater was collected every hour over 2- to 3-day periods at Beppu, Japan (33°16′N, 131°29′E), which lies on or close to the typhoon routes. The deuterium excess parameters (δD – 8 ·δ¹⁸O) of the rainwaters vary over wide ranges from 19.22 to 1.52 for Typhoon No. 13, 1993, and from 6.02 to −8.10 for Typhoon No. 6, 1996, respectively. Rainwaters with higher d-values precipitated in the forward parts of the typhoons. This is ascribed to the possibility that the water vapors supplied by the bottom air currents from the front (rear) of the typhoons may be originally formed by rapid (gentle) evaporation of seawater. Symmetrical patterns of spatial δD and δ¹⁸O distributions within the typhoon precipitations, as estimated from the variations in the isotope ratios of the typhoon rainwaters, should appear from a continuous isotopic fractionation of water vapors with the bottom air currents converging toward the typhoon center. The weighted means of δD and δ¹⁸O of the typhoon precipitations are more negative than those of ordinary rainfall, suggesting that an isotopic influence of typhoon precipitation on surface waters, e.g., river, stream, lake, and spring waters, may be important. Received: January 22, 2000 / Accepted: March 24, 2000     

Shigella chromosomal IpaH proteins are secreted via the type III secretion system and act as effectors

Shigella possess 220 kb plasmid, and the major virulence determinants, called effectors, and the type III secretion system (TTSS) are exclusively encoded by the plasmid. The genome sequences of S. flexneri strains indicate that several ipaH family genes are located on both the plasmid and the chromosome, but whether their chromosomal IpaH cognates can be secreted from Shigella remains unknown. Here we report that S. flexneri strain, YSH6000 encodes seven ipaH cognate genes on the chromosome and that the IpaH proteins are secreted via the TTSS. The secretion kinetics of IpaH proteins by bacteria, however, showed delay compared with those of IpaB, IpaC and IpaD. Expression of the each mRNA of ipaH in Shigella was increased after bacterial entry into epithelial cells, and the IpaH proteins were secreted by intracellular bacteria. Although individual chromosomal ipaH deletion mutants showed no appreciable changes in the pathogenesis in a mouse pulmonary infection model, the DeltaipaH-null mutant, whose chromosome lacks all ipaH genes, was attenuated to mice lethality. Indeed, the histological examination for mouse lungs infected with the DeltaipaH-null showed a greater inflammatory response than induced by wild-type Shigella, suggesting that the chromosomal IpaH proteins act synergistically as effectors to modulate the host inflammatory responses.     

Peptides of type II collagen can induce the cleavage of type II collagen and aggrecan in articular cartilage.

The objective of this study was to determine whether a fragment(s) of type II collagen can induce cartilage degradation. Fragments generated by cyanogen bromide (CB) cleavage of purified bovine type II collagen were separated by HPLC. These fragments together with selected overlapping synthetic peptides were first analysed for their capacity to induce cleavage of type II collagen by collagenases in chondrocyte and explant cultures of healthy adult bovine articular cartilage. Collagen cleavage was measured by immunoassay and degradation of proteoglycan (mainly aggrecan) was determined by analysis of cleavage products of core protein by Western blotting. Gene expression of matrix metalloproteinases MMP-13 and MMP-1 was measured using Real-time PCR. Induction of denaturation of type II collagen in situ in cartilage matrix with exposure of the CB domain was identified with a polyclonal and monoclonal antibodies that only react with this domain in denatured but not native type II collagen. As well as the mixture of CB fragments and peptide CB12, a single synthetic peptide CB12-II (residues 195-218), but not synthetic peptide CB12-IV (residues 231-254), potently and consistently induced in explant cultures at 10 microM and 25 microM, in a time, cell and dose dependent manner, collagenase-induced cleavage of type II collagen accompanied by upregulation of MMP-13 expression but not MMP-1. In isolated chondrocyte cultures CB12-II induced very limited upregulation of MMP-13 as well as MMP-1 expression. Although this was accompanied by concomitant induction of cleavage of type II collagen by collagenases, this was not associated by aggrecan cleavage. Peptide CB12-IV, which had no effect on collagen cleavage, clearly induced aggrecanase specific cleavage of the core protein of this proteoglycan. Thus these events involving matrix molecule cleavage can importantly occur independently of each other, contrary to popular belief. Denaturation of type II collagen with exposure of the CB12-II domain was also shown to be much increased in osteoarthritic human cartilage compared to non-arthritic cartilage. These observations reveal that peptides of type II collagen, to which there is increased exposure in osteoarthritic cartilage, can when present in sufficient concentration induce cleavage of type II collagen (CB12-II) and aggrecan (CB12-IV) accompanied by increased expression of collagenases. Such increased concentrations of denatured collagen are present in adult and osteoarthritic cartilages and the exposure of chondrocytes to the sequences they encode, either in soluble or more likely insoluble form, may therefore play a role in the excessive resorption of matrix molecules that is seen in arthritis and development.