Effect of arena size on behaviour and mortality of the oriental cockroach Blatta orientalis in arenas with a cypermethrin deposit adjacent to harbourage access points

Activity and survival of adult female Blatta orientalis was investigated using tagged cockroaches in periodically illuminated arenas (LD 12:12 h) with a harbourage at one end. The arenas were rectangular with a width of 50 cm and lengths up to 480 cm. A cypermethrin-treated plywood plate (50 × 11 cm) substrate across the harbourage access points caused cockroaches to be exposed to the insecticide deposit by tarsal contact as they entered or left the harbourage. The effects of varying arena length and cypermethrin concentration were tested at 28°C. The LC50 following 3 days exposure ranged from 5.7 to 11.8 mg/m² on the plywood plate for arena lengths of 60 to 480 cm, respectively; cypermethrin at 30 mg/m² produced 100% knockdown of B. orientalis within one 12 h dark period.
During darkness, active cockroaches spent most time close to the harbourage or around food and water stations, at the far end of the arena, and made frequent returns into the harbourage. For arena length 120 cm, the mean duration of contact with treated plates during the first hour of the dark period was significantly less than contact time on untreated plates, but during 12 h the cumulative contact times were not significantly different between treated and untreated plates. During the first 4 h of the dark period, mean cockroach numbers on the treated plate declined as arena length increased, but not as rapidly as the mean number/unit area over the rest of the arena. The arena design is considered suitable for comparative testing of fast-acting neuroactive insecticide deposits against cockroaches.     

Localization and Properties of Cell Wall Enzyme Activities Related to the Final Stages of Lignin Biosynthesis

Cell wall activities which are related to the final stages oflignin biosynthesis, that is the generation of hydrogen peroxideand peroxidase activity, were investigated using biochemicaland histochemical methods. Peroxidases involved in both reactionsappeared to be restricted to lignifying tissues. Isolated cellwalls exhibited a very high affinity for syringaldazine. Cellwalls were able, in vitro as well as in vivo, to oxidize guaiacolin the absence of H₂O₂ when NADH was present in the incubationmedium together with p-coumarate and MnCl₂ as cofactors. Theorigin of the NADH used to form H₂O₂ is discussed. Key words: Lignin biosynthesis, Oxidative polymerization, Peroxidases     

Investigation of the 'switch-epitope' concept with random peptide libraries displayed as thioredoxin loop fusions.

The 'FLITRX' random peptide library, consisting of dodecamer loop peptides displayed on a thioredoxin-flagellin scaffold on Escherichia coli, was used to select peptide sequences with affinity for a monoclonal antibody. These peptides were further screened for pH- and metal-sensitive antibody binding. Several zinc-sensitive peptides were identified, termed 'switch epitopes'. A soluble, monomeric thioredoxin loop ('Trxloop') insertion analog of a FLITRX switch epitope was constructed and its antibody binding properties were characterized by Western blots. Zinc-dependent antibody recognition was maintained in the Trxloop protein although the apparent antibody affinity was lower. This Trxloop protein bound to an immobilized metal affinity chromatography matrix, similar to a 'histidine-patch' thioredoxin variant, and was reversibly precipitated by 1 mM Zn(2+) or Cu(2+) ions. Residues important for zinc and antibody binding were determined by site-directed mutagenesis. The Trxloop antibody affinity was increased by saturation mutagenesis. Biotinylated Trxloop ('Biotrxloop') variants of the original and improved affinity Trxloop proteins were constructed and characterized by surface plasmon resonance measurements. Increased antibody affinity was partially due to a slower antibody desorption rate, although the relative adsorption rates were dependent on the amount of immobilized Biotrxloop protein, indicating an influence of avidity on the apparent affinity.     

Conversion of environmental pollutant to mutagens by visible light.

Illumination of DMBA, 3-methylcholanthrene, 2-aminoanthracene and chrysene with visible light resulted in the formation of direct-acting chemicals endowed with genotoxic and frameshift mutagenic activities. These findings may be of relevance in assessing the potential health hazards inherent in the planned conversion to diesel fuels which is expected to result in increased atmospheric levels of polycyclic aromatic hydrocarbons.     

Variation among mouse strains in responsiveness to migration inhibitory factor.

Mineral oil-induced peritoneal exudate cells (PEC) from 10 different inbred mouse strains were tested for their responses to macrophage migration inhibitory factor (MIF). PEC from 5 out of 10 mouse strains responded to MIF, PEC from BALB/c mice showed an intermediate responsiveness, and PEC from A/J, C3H/HeJ, CBA/N, and C57BL/10ScCR mice were refractory to MIF. MIF responsiveness was not linked to the H-2 complex. However, a possible link between responsiveness to LPS and MIF was suggested, since the mouse strains not responding to MIF were previously reported to be deficient for responses to LPS.