Fermentability of the hemicellulose‐derived sugars from steam‐exploded softwood (douglas fir)

Steam explosion ofDouglas fir wood chips under low‐severity conditions (log Ro = 3.08 corresponding to 175°C, 7.5 min, and 4.5% SO₂) resulted in the recovery of around 87% of the original hemicellulose component in the water‐soluble stream. More than 80% of the recovered hemicellulose was in a monomeric form. As the pretreatment severity increased from 3.08 to 3.76, hemicellulose recovery dropped to 43% of the original hemicellulose found in Douglas fir chips while the concentration of glucose originating from cellulose hydrolysis increased along with the concentration of sugar degradation products such as furfural and hydroxymethylfurfural. Despite containing a higher concentration of hexose monomers (mainly glucose originating from cellulose degradation), the water‐soluble fraction prepared under high‐severity conditions (log Ro = 3.73 corresponding to 215°C, 2.38 min, and 2.38% SO₂) was not readily fermented. Only the two hydrolyzates obtained at low and medium (195°C, 4.5 min, and 4.5% SO₂) severities were fermented to ethanol using a spent sulfur liquor adapted strain of Saccharomyces cerevisiae. High ethanol yields were obtained for these two hydrolyzates with 0.44 g of ethanol produced per gram of hexose utilized (86% of theoretical). However, the best results of hemicellulose recovery and fermentability were obtained for the low‐severity water‐soluble fraction which was fermented significantly faster than the fraction obtained after medium‐severity treatment probably because it contained higher amounts of fermentation inhibitors. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 64: 284–289, 1999.     

Screening and evaluation of different algal extracts and prospects for controlling the disease vector mosquito Culex pipiens L.

Continual application of synthetic insecticides in controlling mosquito larvae has resulted in several problems as build-up of mosquito resistance beside to negative impacts on human health and environment. Discovering new and affordable bio-insecticidal agents with high efficiency, cost effective and target specific become a crucial need. The current study assessed the larvicidal activity of eight methanolic algal extracts belong to three different algal divisions against the 3^rd larval instar of Culex pipiens L. (Diptera: Culicidae). Comparative studies showed that four species of red and green algal extracts exhibited good larvicidal activity. Galaxaura elongata and Jania rubens (Rhodophyta), Codium tomentosum and Ulva intestinales (Chlorophyta) showed higher larvicidal potencies than Padina boryana, Dictyota dichotoma, and Sargassum dentifolium (Phaeophyta) and Gelidium latifolium (Rhodophyta). The maximum level of toxicity was achieved by exposure to G. elongata extract with LC₅₀ (31.13 ppm), followed by C. tomentosum (69.85 ppm) then J. rubens (84.82 ppm) and U. intestinalis (97.54 ppm), while the lowest toxicity exhibited by G. latifolium (297.38 ppm) at 72 h post- treatment. The application of LC₅₀ values of G. elongate, J. rubens, C. tomentosum, and U. intestinalis extracts affected the activities of antioxidant enzymes viz. superoxide dismutase, catalase and glutathione peroxidase as oxidative stress markers. An increase of antioxidant enzymes activities was recorded. Therefore, a significant elimination of free radicals, causing toxic effects. Overall, this study casts light on the insecticidal activity of some algal extracts, suggesting the possibility of application of these bio- agents as novel and cost- effective larvicides.     

Schistosoma mansoni infection induces plasmablast and plasma cell death in the bone marrow and accelerates the decline of host vaccine responses

Schistosomiasis is a potentially lethal parasitic disease that profoundly impacts systemic immune function in chronically infected hosts through mechanisms that remain unknown. Given the immunoregulatory dysregulation experienced in infected individuals, this study examined the impact of chronic schistosomiasis on the sustainability of vaccine-induced immunity in both children living in endemic areas and experimental infections in mice. Data show that chronic Schistosoma mansoni infection impaired the persistence of vaccine specific antibody responses in poliovirus-vaccinated humans and mice. Mechanistically, schistosomiasis primarily fostered plasmablast and plasma cell death in the bone marrow and removal of parasites following praziquantel treatment reversed the observed cell death and partially restored vaccine-induced memory responses associated with increased serum anti-polio antibody responses. Our findings strongly suggest a previously unrecognized mechanism to explain how chronic schistosomiasis interferes with an otherwise effective vaccine regimen and further advocates for therapeutic intervention strategies that reduce schistosomiasis burden in endemic areas prior to vaccination.     

Neurobiology: Paper alert

A selection of interesting papers that were published in the two months before our press date in major journals most likely to report significant results in neurobiology.     

A continuous restriction map from HLA-E to HLA-F. Structural comparison between different HLA-A haplotypes

The class I region of the human major histocompatibility complex contains genes encoding the classical transplantation antigens (HLA-A, B, and C), at least three new class I genes (HLA-E, F, and G) and many class I pseudogenes (including HLA-H). By pulse field gel electrophoresis and using five rare cutter enzymes, we have constructed a precise and continuous map of 1200 kilobases (kb) around HLA-A. The blots were hybridized with HLA-A, E, and F-specific probes and with new probes derived from yeast artificial chromosomes and cosmids of the class I region. We have compared the genomic organization of the same 1200 kb in three homozygous lymphoblastoid cell lines corresponding to three different HLA haplotypes (A3, A24, and A31). The differences in size observed may have been caused by insertions and deletions and may prove valuable in understanding the evolution of the HLA chromosomal region.     

Effect of form and level of applied nitrogen on nitrogenase and nitrate reductase activities in faba beans

The effects of nitrogen applied at increasing levels of 0, 4, 8, 16 and 32 mM N (KNO₃ or NH₄Cl) were studied in faba bean (Vicia faba) nodulated byRhizobium leguminosarum bv.viceae RCR lool. Nitrogenase activity was higher at 4 and 8 mM N than the zero N treatment (control), but 16 and 32 mM N significantly reduced the efficiency of nodule functions. Nitrate reductase activities (NRA) of leaves, stems, roots, nodules and nodule fractions (bacteroid and cytosol) were increased with rising the NO₃ ^? or NH₄ ⁺ levels. NRA decreased in the order of nodules>leaves>stems>roots. Cytosolic NR was markedly higher than that recorded in the bacteroid fractions. Nitrate levels were linearly correlated to NRA of nodules. Accumulation of NO₂ ^? within nodules suggests that NO₂ ^? inhibits nodule’s activity after feeding plants with NO₃ ^? or NH₄ ⁺.     

Algal flora of certain gravel pits in the Thames Valley,U.K.

Summary Detailed analyses are presented of the phytoplankton of two pairs of gravel pits in the Surrey-Middlesex area of the Thames Valley. One of each pair has been recently excavated while the other is much older.Gravel dredging was fairly localised during the investigation, so that it was possible to study an area of disturbed water and an area of undisturbed water in each pit.The distribution of the algae in general and the frequency of the principal members of the phytoplankton were correlated, as far as possible with the physical and chemical features of the environment.Certain algae were found to favour the new or alternatively the old pits and there was some indication that some of the algae recorded in larger numbers thrived best in the disturbed or otherwise the undisturbed water of a pit.The total number of species observed in the new pits was considerably smaller than that in the old pits. Estimates of the total phytoplankton indicates that the new pits are richer, but less varied than the old pits.All the pits were flooded once by Thames water during the course of the investigation. Reasons are given for concluding that this flooding did not cause undue contamination with river phytoplankton.     

Ethylene biosynthesis and strigol-induced germination of Striga asiatica

Germination of witchweed [ Striga asiatica (L.) Kuntze], an important parasite on cereal crops, is stimulated by several natural and synthetic compounds. In the present study the role of ethylene in germination of Striga asiatica in response to strigol was examined. Unconditioned seeds and those conditioned for 3 days produced negligible amounts of ethylene in response to strigol. However, extending the conditioning period to 5 and 8 days increased ethylene evolution by more than 10-fold. Ethylene production preceded radicle protrusion and was detectable within 3h after treatment. No germination was observed in the first 6 h of exposure to strigol. Germination and ethylene production increased with strigol concentration. Strigol-induced germination was considerably reduced by the ethylene action inhibitors. 2. 5-norbornadiene, silver thiosulphate and CO₂. The ethylene precursor 1-aminocyclopropane-1-carboxyac acid (ACC) at 5 to 200 μ M elicited neither germination nor ethylene production. However, a combination of strigol and ACC resulted in a high germination rate and copious ethylene production. Both germination and ethylene production were reduced by CoCl₂ and cyclobeximide, inhibitors of the ethylene-forming enzyme and of protein synthesis, respectively. The results are consistent with a model in which conditioning and strigol are required to remove a restriction on the ethylene biosynthetic pathway and in which the ethylene-forming enzyme is rate limiting.     

The epigenetic regulator BRD4 is required for myofibroblast differentiation of knee fibroblasts

Arthrofibrosis, which is characterized by excessive scar tissue and limited motion, can complicate the daily functioning of patients after total knee arthroplasty (TKA). Molecular hallmarks of arthrofibrosis include pathologic accumulation of myofibroblasts and disproportionate collagen deposition. Epigenetic mechanisms, including posttranslation modification of histones, control gene expression and may regulate fibrotic events. This study assessed the role of the bromodomain and extra-terminal (BET) proteins on myofibroblast differentiation. This group of epigenetic regulators recognize acetylated lysines and are targeted by a class of drugs known as BET inhibitors. RNA-seq analysis revealed robust mRNA expression of three BET members (BRD2, BRD3, and BRD4) while the fourth member (BRDT) is not expressed in primary TKA knee outgrowth fibroblasts. RT-qPCR and western blot analyses revealed that BET inhibition with the small molecule JQ1 impairs TGFβ1-induced expression of ACTA2, a key myofibroblast marker, in primary outgrowth knee fibroblasts. Similarly, JQ1 administration also reduced COL3A1 mRNA levels and collagen deposition as monitored by picrosirius red staining. Interestingly, the inhibitory effects of JQ1 on ACTA2 mRNA and protein expression, as well as COL3A1 expression and collagen deposition, were paralleled by siRNA-mediated depletion of BRD4. Together, these data reveal that BRD4-mediated epigenetic events support TGFβ1-mediated myofibroblast differentiation and collagen deposition as seen in arthrofibrosis. To our knowledge, these are the first studies that assess epigenetic regulators and their downstream events in the context of arthrofibrosis. Future studies may reveal clinical utility for drugs that target epigenetic pathways, specifically BET proteins, in the prevention and treatment of arthrofibrosis.     

Biology and development of some stored grain pests as affected by δ‐endotoxin and β‐exotoxin of Bacillus thuringiensis

Exposure of Plodia interpunctella and Sitotroga cerealella to sublethal concentrations of Dipel 2X® (Bacillus thuringiensis var.kurstaki‐HD‐1)with its spores and endotoxin crystals led to an increase in the sum of larval‐pupal duration. A decrease in moth emergence, egg production and fertility was observed with increase of Dipel 2X concentration, while the longevity of the moths was not affected by treatment. Sublethal concentrations of β‐exotoxin (ABG‐6162 A) had no significant effect on the sum of larval—pupal duration of either insect species. Percentage of moth emergence decreased with the increase of β‐exotoxin concentrations. The longevity of both male and female adults of P. interpunctella and of females of S. cerealella were shorter at high concentrations. Egg production in P. interpunctella was reduced by all concentrations of the β‐exotoxin, and hatching of eggs was reduced by concentrations of 15 ppm and above.