Resilience of a forest fragment exposed to long-term isolation in Singapore

Background: Fragmentation can fundamentally alter the structure of tropical forests. However, the impacts of fragmentation may vary significantly among regions and lead to different outcomes.

Aims: We examined the structure, composition and dynamics of a forest fragment in Singapore to investigate reasons for the apparent resilience of this forest to long-term isolation.

Methods: We conducted 5 censuses of 12,688 trees ≥1-cm dbh in a 2-ha plot on the edge of the fragment between 1993 and 2012.

Results: Stem density and basal area were not significantly different between 1993 and 2012 and were typical of other south-east Asian forests. However, there were short-term decreases in both variables after droughts in 1997 and 2009, both followed by recovery. Total mortality rate over the 19 years was 3.3% year^?1, considerably higher than other tropical forests in Asia, but it was balanced by high recruitment. The 10 most abundant species were primary forest species, pioneer species comprised <5% of all stems, and none of the 338 species in the plot was exotic. However, species abundances changed more than expected by chance for 86 species, and the rank order of the commonest species changed significantly. Species abundance changes were not related to known species traits.

Conclusions: Despite the long period of isolation, we found a surprising level of resilience of the Bukit Timah forest. While the forest may be more sensitive to the effects of climatic fluctuations at decadal time scales, there were very few signs of forest degradation in this diverse fragment of tropical forest.     

Non-specific phospholipases C2 and C6 redundantly function in pollen tube growth via triacylglycerol production in Arabidopsis

Non-specific phospholipase Cs (NPCs) are responsible for membrane lipid remodeling that involves hydrolysis of the polar head group of membrane phospholipids. Arabidopsis NPC2 and NPC6 are essential in gametogenesis, but their underlying role in the lipid remodeling remains elusive. Here, we show that these NPCs are required for triacylglycerol (TAG) production in pollen tube growth. NPC2 and NPC6 are highly expressed in developing pollen tubes and are localized at the endoplasmic reticulum. Mutants of NPC2 and NPC6 showed reduced rate of pollen germination, length of pollen tube and amount of lipid droplets (LDs). Overexpression of NPC2 or NPC6 induced LD accumulation, which suggests that these NPCs are involved in LD production. Furthermore, mutants defective in the biosynthesis of TAG, a major component of LDs, showed defective pollen tube growth. These results suggest that NPC2 and NPC6 are essential in gametogenesis for a role in hydrolyzing phospholipids and producing TAG required for pollen tube growth. Thus, lipid remodeling from phospholipids to TAG during pollen tube growth represents an emerging role for the NPC family in plant developmental control.     

Silver staining of collagen fibrils in cartilage

Summary Direct visualization of individual collagen fibrils by light microscopy in human cartilage was achieved by applying a periodic acid-silver methenamine stain on plastic sections. Collagen fibrils, 100 nm in diameter or thicker, were delineated individually by light microscopy and were easily traced for a length beyond 100m. Thinner fibrils not readily visible optically were identified if arranged in compact bundles as occurring in the superficial zone of articular cartilage.     

Rapidly diminishing mangrove forests in Myanmar (Burma): a review

IPCC predictions indicate an increase in temperatures by 1.5–7°C in some Amazonian regions during the twenty-first century. These changes could disrupt the present distribution patterns of organisms, including wetland plant species. In this work, we determined in microcosms the effects of scenarios combining elevated temperature and atmospheric CO₂ concentration on the germination and initial growth of the arborescent Amazonian aquatic macrophyte Montrichardia arborescens. Seeds were germinated, and seedlings produced were monitored over a 5-month period in four microcosms: Control: ambient temperature and CO₂ level; Mild: Control + 1.5°C and + 200 ppm CO₂; intermediate: control + 2.5°C and + 400 ppm CO₂; Extreme: Control + 4.5°C and + 850 ppm of CO₂. Rapid light response curves and Fv/Fm values taken in seedlings showed a decrease in electron transportation rate with CO₂ and temperature elevation. Mild and Intermediate treatments stimulated biomass production; Extreme treatment and Control produced similar results. The severe climatic changes expected in the future may negatively influence carbon accumulation in M. arborescens. Since aquatic macrophytes in Amazonian wetlands and wetlands worldwide are key plant species, further studies are needed to predict their fate in a global change perspective.     

Potent human glutaminyl cyclase inhibitors as potential anti-Alzheimer’s agents: Structure-activity relationship study of Arg-mimetic region

Pyroglutamate-modified amyloid β peptides (pGlu-Aβ) are highly neurotoxic and promote the formation of amyloid plaques. The pGlu-Aβ peptides are generated by glutaminyl cyclase (QC), and recent clinical studies indicate that QC represents an alternative therapeutic target to treat Alzheimer’s disease (AD). We have previously developed a series of QC inhibitors with an extended pharmacophoric scaffold, termed the Arg-mimetic D-region. In the present study, we focused on the structure activity relationship (SAR) of analogues with modifications in the D-region and evaluated their biological activity. Most compounds in this series exhibited potent activity in vitro, and our SAR analysis and the molecular docking studies identified compound 202 as a potential candidate because it forms an additional hydrophobic interaction in the hQC active site. Overall, our study provides valuable insights into the Arg-mimetic pharmacophore that will guide the design of novel QC inhibitors as potential treatments for AD.     

Assignment of the S-antigen gene (SAG) to human chromosome 2q24-q37

We report the mapping of the gene coding for the S-antigen (48-kDa protein) to human chromosome 2 using somatic cell hybrids. In situ hybridization further confirms this assignment and regionally maps the gene to 2q24-q37.     

A simple spectrophotometric determination of solid supported amino groups

A simple spectrophotometric method for the quantitative determination of solid phase supported amino groups is described. The method involves reacting the solid support with an excess of activated acylating agent, N-succinimidyl-3-(2-pyridyldithio)propionate (SPDP) and an efficient acylation catalyst, 4-dimethylaminopyridine, and after thoroughly removing the unreacted SPDP, the solid support is reacted with an excess of dithiothreitol to quantitatively release pyridine-2-thione from the solid support to the solution. After an appropriate dilution, the released pyridine-2-thione which has a strong absorbance at 343 nm, is quantified by reading its absorbance in a spectrophotometer at 343 nm.     

Strategies for detecting restriction polymorphisms of Y chromosome sequences

Six cloned genomic sequences from the human Y chromosome were used for the detection of restriction polymorphisms in a panel of unrelated DNAs. Three sorts of strategies for the detection of polymorphisms were used: (a) mixing individual DNAs restricted by several endonucleases, (b) separated restrictions of the DNA library members with six different restriction enzymes, (c) individual DNA digestion with TaqI and MsqI. Results show that restriction polymorphisms are detected only rarely; this result can be explained by exemption of most of the Y chromosome from meiotic pairing and exchange.     

Polyethylene beads as supports for enzyme immobilization

Summary Acid oxidation of polyethylene beads generated surface carboxylic groups which were reacted with excess ethylenediamine via carbodiimide promoted reactions. Glucose oxidase was covalently immobilized on the amine substituted beads using either glutaraldehyde, triazine trichloride, or dimethylsuberimidate as crosslinkers. The kinetic properties, pH-profile and the stability of the immobilized enzymes were reported.