Does correlation of cellulase gene expression and cellulolytic activity in the gut of termite suggest synergistic collaboration of cellulases?

Termites play an important role in degradation of dead plant materials in nature. Over the last century, many researchers have investigated the mechanisms of their lignocellulose digesting system. A recent publication by Zhou et al. (Zhou, X., Smith, J.A., Oi, F.M., Koehler, P.G., Bennett, G.W., Scharf, M.E., 2007. Correlation of cellulase gene expression and cellulolytic activity throughout the gut of the termite Reticulitermes flavipes. Gene 395, 29-39) dealt with the cellulolytic system of the flagellate-harboring termite R. flavipes and suggested "the presence of a single unified cellulose digestion system" in the termite, as an alternative hypothesis of a "dual (i.e. endogenous and symbiotic) cellulose digesting system" proposed by Nakashima et al. (Nakashima, K., Watanabe, H., Saitoh, H., Tokuda, G., Azuma, J.-I., 2002. Dual cellulose-digesting system of the wood-feeding termite, Coptotermes formosanus Shiraki. Insect Biochem. Mol. Biol. 32, 777-784). Here we show that their results actually support a dual cellulose digesting system rather than "a single unified cellulose digestion system". In addition, potential problems with their results are highlighted.     

Effects of acid exposure on the conformation, stability, and aggregation of monoclonal antibodies

Exposure of antibodies to low pH is often unavoidable for purification and viral clearance. The conformation and stability of two humanized monoclonal antibodies (hIgG4-A and -B) directed against different antigens and a mouse monoclonal antibody (mIgG1) in 0.1M citrate at acidic pH were studied using circular dichroism (CD), differential scanning calorimetry (DSC), and sedimentation velocity. Near- and far-UV CD spectra showed that exposure of these antibodies to pH 2.7-3.9 induced only limited conformational changes, although the changes were greater at the lower pH. However, the acid conformation is far from unfolded or so-called molten globule structure. Incubation of hIgG4-A at pH 2.7 and 3.5 at 4 degrees C over the course of 24 h caused little change in the near-UV CD spectra, indicating that the acid conformation is stable. Sedimentation velocity showed that the hIgG4-A is largely monomeric at pH 2.7 and 3.5 as well as at pH 6.0. No time-dependent changes in sedimentation profile occurred upon incubation at these low pHs, consistent with the conformational stability observed by CD. The sedimentation coefficient of the monomer at pH 2.7 or 3.5 again suggested that no gross conformational changes occur at these pHs. DSC analysis of the antibodies showed thermal unfolding at pH 2.7-3.9 as well as at pH 6.0, but with decreased melting temperatures at the lower pH. These results are consistent with the view that the antibodies undergo limited conformational change, and that incubation at 4 degrees C at low pH results in no time-dependent conformational changes. Titration of hIgG4-A from pH 3.5 to 6.0 resulted in recovery of native monomeric proteins whose CD and DSC profiles resembled those of the original sample. However, titration from pH 2.7 resulted in lower recovery of monomeric antibody, indicating that the greater conformational changes observed at this pH cannot be fully reversed to the native structure by a simple pH titration.     

Hepatic oxidative DNA damage correlates with iron overload in chronic hepatitis C patients

Hepatic oxidative stress occurs in chronic hepatitis C (CH-C), but little is known about its producing mechanisms and precise role in the pathogenesis of the disease. To determine the relevance of hepatic oxidatively generated DNA damage in CH-C, 8-hydroxy-2'-deoxyguanosine (8-OHdG) adducts were quantified in liver biopsy specimens by immunohistochemical staining, and its relationship with clinical, biochemical, and histological parameters, and treatment response was assessed in 40 CH-C patients. Hepatic 8-OHdG counts were significantly correlated with serum transaminase levels (r=0.560, p=0.0005) and histological grading activity (p=0.0013). Remarkably, 8-OHdG levels were also significantly related to body and hepatic iron storage markers (vs serum ferritin, r=0.565, p=0.0004; vs hepatic total iron score, r=0.403, p=0.0119; vs hepatic hepcidin messenger RNA, r=0.516, p=0.0013). Baseline hepatic oxidative stress was more prominent in nonsustained virological responder (non-SVR) than in SVR to interferon (IFN)/ribavirin treatment (50.8 vs 32.7 cells/10(5) microm2, p=0.0086). After phlebotomy, hepatic 8-OHdG levels were significantly reduced from 53.4 to 21.1 cells/10(5) microm2 (p=0.0125) with concomitant reductions of serum transaminase and iron-related markers in CH-C patients. In conclusion, this study showed that hepatic oxidatively generated DNA damage frequently occurs and is strongly associated with increased iron deposition and hepatic inflammation in CH-C patients, suggesting that iron overload is an important mediator of hepatic oxidative stress and disease progression in chronic HCV infection.     

Sex pheromone production in the silkworm, Bombyx mori, is mediated by store-operated Ca2+ channels

In most female moths, pheromone biosynthesis activating neuropeptide (PBAN) regulates sex pheromone production by stimulating an influx of extracellular Ca(2+). Little is known about the plasma membrane channel or how the PBAN stimulus is communicated to the channel. Fluorescent Ca(2+) imaging techniques confirmed PBAN-induced Ca(2+) influx in the silkworm, Bombyx mori, and showed that the PBAN response is reduced with repeated stimulation. Compounds known to impact Ca(2+) signaling were examined for their effects on sex pheromone production. These experiments demonstrated that the PBAN signal is likely mediated by a store-operated channel (SOC). SOC blockers, SKF-96365 and 2-aminoethoxydiphenyl borate, abolished sex pheromone production, as did flufenamic acid, a blocker of transient receptor potential (TRP) channels. Thapsigargin mimicked the pheromonotropic effects of PBAN. Similar results were seen when PBAN-induced lipase activity was assayed. Conversely, 1-oleoyl-2-acetyl-sn-glycerol and arachidonic acid, activators of diacylglycerol-dependent Ca(2+) channels, had no effect on bombykol production.     

Non-fucosylated therapeutic antibodies: the next generation of therapeutic antibodies

Therapeutic antibody IgG1 has two N-linked oligosaccharide chains bound to the Fc region. The oligosaccharides are of the complex biantennary type, composed of a trimannosyl core structure with the presence or absence of core fucose, bisecting N-acetylglucosamine (GlcNAc), galactose, and terminal sialic acid, which gives rise to structural heterogeneity. Both human serum IgG and therapeutic antibodies are well known to be heavily fucosylated. Recently, antibody-dependent cellular cytotoxicity (ADCC), a lytic attack on antibody-targeted cells, has been found to be one of the critical effector functions responsible for the clinical efficacy of therapeutic antibodies such as anti-CD20 IgG1 rituximab (Rituxan^®) and anti-Her2/neu IgG1 trastuzumab (Herceptin^®). ADCC is triggered upon the binding of lymphocyte receptors (FcγRs) to the antibody Fc region. The activity is dependent on the amount of fucose attached to the innermost GlcNAc of N-linked Fc oligosaccharide via an α-1,6-linkage, and is dramatically enhanced by a reduction in fucose. Non-fucosylated therapeutic antibodies show more potent efficacy than their fucosylated counterparts both in vitro and in vivo, and are not likely to be immunogenic because their carbohydrate structures are a normal component of natural human serum IgG. Thus, the application of non-fucosylated antibodies is expected to be a powerful and elegant approach to the design of the next generation therapeutic antibodies with improved efficacy. In this review, we discuss the importance of the oligosaccharides attached to the Fc region of therapeutic antibodies, especially regarding the inhibitory effect of fucosylated therapeutic antibodies on the efficacy of non-fucosylated counterparts in one medical agent. The impact of completely non-fucosylated therapeutic antibodies on therapeutic fields will be also discussed.     

Association of cathepsin E with tumor growth arrest through angiogenesis inhibition and enhanced immune responses

Cathepsin E (CE) is an intracellular aspartic proteinase implicated in various physiological and pathological processes, yet its actual roles in vivo remain elusive. To assess the physiological significance of CE expression in tumor cells, human CE was stably expressed in human prostate carcinoma ALVA101 cells expressing very little CE activity. Tumor growth in nude mice with xenografted ALVA101/hCE cells was slower than with control ALVA101/mock cells. Angiogenesis antibody array and ELISA assay showed that this was partly due to the increased expression of some antiangiogenic molecules including interleukin 12 and endostatin in tumors induced by CE expression. In vitro studies also demonstrated that, among the cathepsins tested, CE most efficiently generated endostatin from the non-collagenous fragment of human collagen XVIII at mild acidic pH. Histological examination revealed that tumors formed by ALVA101/hCE cells were partitioned by well-developed membranous structures and covered with thickened, well-stratified hypodermal tissues. In addition, both the number and extent of activation of tumor-infiltrating macrophages were more profound in ALVA101/hCE compared to ALVA101/mock tumors. The chemotactic response of macrophages to ALVA101/hCE cells was also higher than that to ALVA/mock cells. These results thus indicate that CE expression in tumor cells induces tumor growth arrest via inhibition of angiogenesis and enhanced immune responses.     

Temporally explicit abiotic depletion potential (TADP) for mineral resource use based on future demand projections

Purpose

Assessing the potential impacts (characterization) of mineral resource use in life cycle impact assessment (LCIA) has long been debated. One of the most crucial challenges in the characterization models for mineral resource use is the consideration of the changing demand and availability of in-use stocks in the future, which is relevant to the global population and economy growth as well as the increasing low-carbon technologies. We propose an extended characterization model to assess the potential impacts for arbitrary time horizons, considering future demand changes and the availability of in-use stock: temporally explicit abiotic depletion potential (TADP).

Methods

The TADP was developed based on abiotic depletion potential (ADP), which is a widely used characterization model for mineral resource use. While the ADP assesses the potential impacts of mineral resource use based on a natural stock estimate and the current extraction rate, the TADP adopts an average extraction rate for arbitrary time horizons. The average extraction rate was estimated using material flow analysis considering future demand changes and recycling under the five shared socioeconomic pathways (SSPs). TADPs were calculated for six common metals: aluminum, copper, iron, lead, nickel, and zinc.

Results and discussion

As a result of calculating TADPs for the term by 2050 (TADP₂₀₅₀), compared to iron, all other metals showed larger values of characterization factors for all SSPs than the original ADPs. The TADP₂₀₅₀ of copper exhibited the largest difference with ADP among the six metals (approximately 1.9 times), which is mainly attributed to future demand growth. On the other hand, for the longer time perspective, the TADP₂₁₀₀ of lead and zinc exhibited larger differences with ADP than copper (approximately 2.8 times for zinc), which is mainly due to a relatively shorter lifetime for lead and a lower recycling rate for zinc. This suggests that the relative significance of the characterization factors of metals varies depending on the temporal perspective.

Conclusions

With the proposed characterization model, the potential impacts of mineral resource use can be assessed reflecting future situations for the selected time horizons. The results demonstrate that the consideration of future situations greatly influences the relative significance of the potential impacts of using different mineral resources in the results of LCIA studies. By expanding the coverage of mineral resources and future scenario analysis to other relevant factors, the TADP model can improve the robustness of the assessment and further support decision-making towards sustainable resource management.