Changes in Soil Carbon and Nitrogen following Land Abandonment of Farmland on the Loess Plateau,China

The revegetation of abandoned farmland significantly influences soil organic C (SOC) and total N (TN). However, the dynamics of both soil OC and N storage following the abandonment of farmland are not well understood. To learn more about soil C and N storages dynamics 30 years after the conversion of farmland to grassland, we measured SOC and TN content in paired grassland and farmland sites in the Zhifanggou watershed on the Loess Plateau, China. The grassland sites were established on farmland abandoned for 1, 7, 13, 20, and 30 years. Top soil OC and TN were higher in older grassland, especially in the 0–5 cm soil depths; deeper soil OC and TN was lower in younger grasslands (<20 yr), and higher in older grasslands (30 yr). Soil OC and N storage (0–100 cm) was significantly lower in the younger grasslands (<20 yr), had increased in the older grasslands (30 yr), and at 30 years SOC had increased to pre-abandonment levels. For a thirty year period following abandonment the soil C/N value remained at 10. Our results indicate that soil C and TN were significantly and positively correlated, indicating that studies on the storage of soil OC and TN needs to focus on deeper soil and not be restricted to the uppermost (0–30 cm) soil levels.     

Multi-Functional Roles of Chitosan as a Potential Protective Agent against Obesity

Chitosan, a natural polysaccharide comprising copolymers of glucosamine and N-acetylglucosamine, has been shown to have anti-obesity properties. Two experiments (Exp. 1 and Exp. 2) were performed to determine the role of chitosan on dietary intake, body weight gain, and fat deposition in a pig model, as well as identifying potential mechanisms underlying the anti-obesity effect of chitosan. In Exp. 1, the nutrient digestibility experiment, 16 pigs (n = 4/treatment) were randomly allocated to one of four dietary treatments as follows: 1) basal diet; 2) basal diet plus 300 ppm chitosan; 3) basal diet plus 600 ppm chitosan; 4) basal diet plus 1200 ppm chitosan. The main observation was that crude fat digestibility was lower in the 1200 ppm chitosan group when compared with the control group (P<0.05). In Exp. 2, a total of 80 pigs (n = 20/treatment) were offered identical dietary treatments to that offered to animals in Exp. 1. Blood samples were collected on day 0, day 35 and at the end of the experiment (day 57). Animals offered diets containing 1200 ppm chitosan had a lower daily dietary intake (P<0.001) and body weight gain (P<0.001) from day 35 to 57 when compared with all the other treatment groups. Animals offered diets containing 1200 ppm chitosan had a significantly lower final body weight (P<0.01) when compared with all the other treatment groups. The decreased dietary intake observed in the 1200 ppm chitosan group was associated with increased serum leptin concentrations (P<0.001) and a decrease in serum C-reactive protein (CRP) concentrations (P<0.05). In conclusion, the results of this study highlight novel endocrine mechanisms involving the modulation of serum leptin and CRP concentrations by which chitosan exhibits anti-obesity properties in vivo.     

A Clinical,Neuropathological and Genetic Study of Homozygous A467T POLG-Related Mitochondrial Disease

Mutations in the nuclear gene POLG (encoding the catalytic subunit of DNA polymerase gamma) are an important cause of mitochondrial disease. The most common POLG mutation, A467T, appears to exhibit considerable phenotypic heterogeneity. The mechanism by which this single genetic defect results in such clinical diversity remains unclear. In this study we evaluate the clinical, neuropathological and mitochondrial genetic features of four unrelated patients with homozygous A467T mutations. One patient presented with the severe and lethal Alpers-Huttenlocher syndrome, which was confirmed on neuropathology, and was found to have a depletion of mitochondrial DNA (mtDNA). Of the remaining three patients, one presented with mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS), one with a phenotype in the Myoclonic Epilepsy, Myopathy and Sensory Ataxia (MEMSA) spectrum and one with Sensory Ataxic Neuropathy, Dysarthria and Ophthalmoplegia (SANDO). All three had secondary accumulation of multiple mtDNA deletions. Complete sequence analysis of muscle mtDNA using the MitoChip resequencing chip in all four cases demonstrated significant variation in mtDNA, including a pathogenic MT-ND5 mutation in one patient. These data highlight the variable and overlapping clinical and neuropathological phenotypes and downstream molecular defects caused by the A467T mutation, which may result from factors such as the mtDNA genetic background, nuclear genetic modifiers and environmental stressors.     

The quantification of erlotinib (OSI-774) and OSI-420 in human plasma by liquid chromatography-tandem mass spectrometry

An accurate and precise method was developed using HPLC-MS/MS to quantify erlotinib (OSI-774) and its O-desmethyl metabolite, OSI-420, in plasma. The advantages of this method include the use of a small sample volume, liquid-liquid extraction with high extraction efficiency and short chromatographic run times. The analytes were extracted from 100 microL plasma volume using hexane:ethyl acetate after midazolam was added to the sample for internal standardization. The compounds were separated on a Phenomenex C-18 Luna analytical column with acetonitrile:5 mM ammonium acetate as the mobile phase. All compounds were monitored by tandem mass spectrometry with electrospray positive ionization. The intra-day accuracy and precision (% coefficient of variation, % CV) estimates for erlotinib at 10 ng/mL were 90% and 9%, respectively. The intra-day accuracy and precision estimates for OSI-420 at 5 ng/mL were 80% and 4%, respectively. This method was used to quantify erlotinib and OSI-420 in plasma of patients (n=21) administered 150 mg erlotinib per day for non-small cell lung cancer.     

Comparative visual acuity of coleoid cephalopods

The pelagic realm of the ocean is characterized by extremelyclear water and a lack of surfaces. Adaptations to the visualecology of this environment include transparency, fluorescence,bioluminescence, and deep red or black pigmentation. While thesignals that pelagic organisms send are increasingly well-understood,the optical capabilities of their viewers, especially for predatorswith camera-like vision such as fish and squid, are almost unknown.Aquatic camera-like vision is characterized by a spherical lensfocusing an image on the retina. Here, we measured the resolvingpower of the lenses of eight species of pelagic cephalopodsto obtain an approximation of their visual capabilities. Wedid this by focusing a standard resolution target through dissectedlenses and calculating their modulation transfer functions.The modulation transfer function (MTF) is the single most completeexpression of the resolving capabilities of a lens. Since theoptical and retinal capabilities of an eye are generally well-matched,we considered our measurements of cephalopod lens MTF to bea good proxy for their visual capabilities in vivo. In general,squid have optical capabilities comparable to other organismsgenerally assumed to have good vision, such as fish and birds.Surprisingly, the optical capability of the eye of Vampyroteuthisinfernalis rivals that of humans.     

Bicaudal‐D binds clathrin heavy chain to promote its transport and augments synaptic vesicle recycling

Cargo transport by microtubule‐based motors is essential for cell organisation and function. The Bicaudal‐D (BicD) protein participates in the transport of a subset of cargoes by the minus‐end‐directed motor dynein, although the full extent of its functions is unclear. In this study, we report that in Drosophila zygotic BicD function is only obligatory in the nervous system. Clathrin heavy chain (Chc), a major constituent of coated pits and vesicles, is the most abundant protein co‐precipitated with BicD from head extracts. BicD binds Chc directly and interacts genetically with components of the pathway for clathrin‐mediated membrane trafficking. Directed transport and subcellular localisation of Chc is strongly perturbed in BicD mutant presynaptic boutons. Functional assays show that BicD and dynein are essential for the maintenance of normal levels of neurotransmission specifically during high‐frequency electrical stimulation and that this is associated with a reduced rate of recycling of internalised synaptic membrane. Our results implicate BicD as a new player in clathrin‐associated trafficking processes and show a novel requirement for microtubule‐based motor transport in the synaptic vesicle cycle.     

Inhibition of mono-ADP-ribosyltransferase activity during the execution phase of apoptosis prevents apoptotic body formation

The objective of this study was to understand factors responsible for apoptotic body formation and release during apoptosis. We have found that inhibition of mono-ADP ribosylation after ultraviolet (UV) light induction of apoptosis in HL-60 cells does not block caspase-3 activation, gelsolin cleavage, or endonucleolytic DNA fragmentation. However, the cytoskeletal features of apoptosis leading to apoptotic body formation and release were inhibited by meta-iodobenzylguanidine (MIBG) and novobiocin, potent inhibitors of arginine-specific mono-ADP-ribosyltransferases (mono-ADPRTs). Suppression of mono-ADP ribosylation as late as 120 min following UV irradiation blocked the depolymerization of actin and release of apoptotic bodies. This suggested that the cytoskeletal changes of apoptosis may be decoupled from the caspase cascade and that there may be a biochemical event either distal to or independent of caspase-3 that regulates apoptotic body formation. To test the hypothesis that ADP ribosylation of actin may occur with the induction of apoptosis, an in vivo assay of mono-ADPRT activity using an antibody against ADP-ribosylarginine was used. An approximately 64% increase in the ADP ribosylation of actin was observed at 2 h following exposure to UV light. When MIBG or novobiocin was present, the ADP ribosylation of actin was only 14-18% above the levels observed in control nonirradiated cells. The current study is the first to demonstrate a relationship between ADP-ribosylation of actin and the formation of apoptotic bodies.     

The role of human glutathione S-transferases (hGSTs) in the detoxification of the food-derived carcinogen metabolite N-acetoxy-PhIP, and the effect of a polymorphism in hGSTA1 on colorectal cancer risk

Food-derived heterocyclic amines (HCAs), particularly 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), are implicated in the etiology of human colorectal cancer (CRC) via a process of N-oxidation followed by O-acetylation or O-sulfation to form electrophilic metabolites that react with DNA. Glutathione S-transferases (GSTs) detoxify activated carcinogen metabolites by catalysis of their reaction with GSH. However, among HCAs, only N-acetoxy-PhIP has been shown to be a substrate for the GSTs. By using a competitive DNA-binding assay, we confirm that hGSTA1-1 is an efficient catalyst of the detoxification of N-acetoxy-PhIP. Further, we show that hGSTs A2-2, P1-1, M1-1, T1-1 and T2-2 appear to have low activity towards N-acetoxy-PhIP, and that hGSTs A4-4, M2-2, M4-4 and Z1-1 appear to have no activity towards N-acetoxy-PhIP. A genetic polymorphism in the 5'-regulatory sequence of hGSTA1 has been shown to correlate with the relative and absolute levels of expression of GSTA1/GSTA2 in human liver. Examination of hGSTA1 allele frequency in 100 Caucasian CRC patients and 226 Caucasian controls demonstrated a significant over-representation of the homozygous hGSTA1*B genotype among cases compared to controls (24.0 and 13.7%, respectively, P=0.04). This corresponds to an odds ratio for risk of CRC of 2.0 (95% CI 1.0-3.7) when comparing homozygous hGSTA1*B individuals with all other genotypes. Thus, individuals who are homozygous hGSTA1*B, and who would be predicted to have the lowest levels of hGSTA1 expression in their livers, appear to be at risk of developing CRC, possibly as a result of inefficient hepatic detoxification of N-acetoxy-PhIP.     

An inhibitor of p38 mitogen-activated protein kinase prevents insulin-stimulated glucose transport but not glucose transporter translocation in 3T3-L1 adipocytes and L6 myotubes

The precise mechanisms underlying insulin-stimulated glucose transport still require investigation. Here we assessed the effect of SB203580, an inhibitor of the p38 MAP kinase family, on insulin-stimulated glucose transport in 3T3-L1 adipocytes and L6 myotubes. We found that SB203580, but not its inactive analogue (SB202474), prevented insulin-stimulated glucose transport in both cell types with an IC50 similar to that for inhibition of p38 MAP kinase (0.6 microM). Basal glucose uptake was not affected. Moreover, SB203580 added only during the transport assay did not inhibit basal or insulin-stimulated transport. SB203580 did not inhibit insulin-stimulated translocation of the glucose transporters GLUT1 or GLUT4 in 3T3-L1 adipocytes as assessed by immunoblotting of subcellular fractions or by immunofluorescence of membrane lawns. L6 muscle cells expressing GLUT4 tagged on an extracellular domain with a Myc epitope (GLUT4myc) were used to assess the functional insertion of GLUT4 into the plasma membrane. SB203580 did not affect the insulin-induced gain in GLUT4myc exposure at the cell surface but largely reduced the stimulation of glucose uptake. SB203580 had no effect on insulin-dependent insulin receptor substrate-1 phosphorylation, association of the p85 subunit of phosphatidylinositol 3-kinase with insulin receptor substrate-1, nor on phosphatidylinositol 3-kinase, Akt1, Akt2, or Akt3 activities in 3T3-L1 adipocytes. In conclusion, in the presence of SB203580, insulin caused normal translocation and cell surface membrane insertion of glucose transporters without stimulating glucose transport. We propose that insulin stimulates two independent signals contributing to stimulation of glucose transport: phosphatidylinositol 3-kinase leads to glucose transporter translocation and a pathway involving p38 MAP kinase leads to activation of the recruited glucose transporter at the membrane.