Effects of long-term storage on potency of TM Biocontrol-1, the registered viral insecticide of Orgyia pseudotsugata (Lepidoptera: Lymantriidae).

The article presents the results of bioassaying 39 samples of TM Biocontrol-1, a viral insecticide, from 10 different lots and various sizes of vacuum-sealed packages that were stored at -10 degrees C for 5-15 yr. This is the first study to present potency data for a registered virus product stored for this length of time. Laboratory bioassays in insects from the same colony from which the TM Biocontrol-1 was produced showed that the stored viral insecticide is still effective, although it lost approximately 30% of its effectiveness during storage. A direct correlation of this loss with the length of time in storage is not apparent. Bioassays also showed that there are significant differences in the susceptibility of Douglas-fir tussock moth, Orgyia pseudotsugata (McDunnough), larvae from different geographic regions to OpMNPV (family Baculoviridae, genus Nucleopolyhedrovirus) infection. Package size did not affect the potency of stored TM Biocontrol-1. There were no clear, significant differences in the effectiveness among lots of TM Biocontrol-1 processed by different organizations.

Vertical transmission of nucleopolyhedrovirus in insects.

A review of the literature on transmission studies of nucleopolyhedroviruses showed that low levels of viral infection were common among studies of pupae of insects but rarer in adults. Virus could be transmitted from parent to progeny and could be found in caterpillars reared from surface-decontaminated eggs. Persistent low levels of infection were observed in many of the studies considered. These could contribute to the persistence of virus in low-density populations, but the dominant source of virus among generations is probably through environmental contamination.

Passive material behavior of granulocytes based on large deformation and recovery after deformation tests.

In order to better understand the in vivo rheologic behavior of white cells, we have studied the time-dependent deformability, recovery, and mechanical activation of blood granulocytes. We have used micropipette aspiration methods to measure the large deformation response and recovery after deformation characteristics of neutrophils as functions of time, temperature, and collecting media. The cell response in the pipette experiment was characterized by three time domains: the first phase was the passive deformation response to the fixed suction pressure; the second phase was an obvious transition from the passive to active motile cellular state where the cell exhibited erratic length changes in the pipette; and the third phase was the steady recovery after the suction pressure had been zeroed. Tests on white cells were carried out with three different anticoagulants to evaluate the effect of calcium on deformation and recovery behavior; also, cells were separated by centrifugation in high molecular weight dextran to determine whether or not collection and separation procedures affected the cell properties. Our results have shown that the passive deformation of granulocytes into the pipette was a continuous flow process with no approach to a static deformation limit. In addition, there was an obvious threshold pressure below which the cell would not deform and enter the micropipette. For suction pressures significantly above the threshold, granulocytes were continuously deformed with a similar functional dependence on time. The coefficient of proportionality between aspiration length and time, as well as the exponent, depended on suction pressure, pipette dimension, and temperature. It was observed that the granulocytes always recovered to the spherical state after deformation, independent of the extent of deformation or location where the cell was aspirated. Based on the recovery behavior, plus the dependence of the pressure threshold on pipette size, we propose the concept that the granulocyte membrane and cortical shell behave like a "contractile surface carpet" under tension, where the cell interior responds passively like a highly viscous liquid. The membrane cortex appears to be subject to a persistent stress (tension) of about 10(-2) dyne/cm. Our observations of passive to active transition in the pipette suction experiment indicated that granulocytes may be stimulated by deformation at room temperature. This study represents the first detailed investigation of the large deformation behavior of granulocytes, and the results indicate a simple structural model to represent the passive rheologic behavior of the granulocyte.

Free energy potential for aggregation of erythrocytes and phosphatidylcholine/phosphatidylserine vesicles in Dextran (36,500 MW) solutions and in plasma.

The free energy potential (affinity) for aggregation of human red blood cells and lipid vesicles in Dextran solutions and blood plasma has been quantitated by measuring to what extent a vesicle is encapsulated by the red cell surface. The free energy reduction per unit area of contact formation (affinity) was computed from the observation of the fractional extent of encapsulation at equilibrium with the use of a relation based on the elastic compliance of the red cell membrane as it is deformed to adhere to the vesicle surface. Micromanipulation methods were used to select and transfer single lipid vesicles (2-3 X 10(-4) cm diameter) from a chamber that contained the vesicle suspension to a separate chamber on the microscope stage that contained red cells in an EDTA buffer with Dextran or whole plasma. The vesicle and a red cell were maneuvered into close proximity and contact allowed to take place without forcing the cells together. To evaluate the effects of surface charge density and steric interactions on aggregation, vesicles were made from mixtures of egg phosphatidylcholine (PC) and bovine phosphatidylserine (PS) over a range of mole ratios (PC/PS)from (1:0) to (1:1); the vesicles were formed by rehydration in buffer. The Dextran solutions were made with a sharp-cut fraction of 36,500 MW in a concentration range of 0-10% by weight in grams (wt/wt). It was found that the Dextran 36,500 MW fraction produced aggregation behavior for red cells and vesicles similar to red cell-red cell aggregation in Dextran 70,000-150,000 MW fractions, when the vesicle surface charge density was comparable with that of normal red cells (i.e., PC/PS ratio of -3:1). This result indicated that Dextran molecules penetrate between the carbohydrate groups on the red cell surface and that either steric interactions between cell surface carbohydrates are important or many of the charge groups on red cells are superficial. Electrostatic repulsion effects were apparent, as no aggregation in Dextran 36,500 MW occurred for PC/PS ratios <2.6:1; the level of affinity increased with the PC content at a specific Dextran concentration. Affinities were measured in the range of 0-2 x 10-2 ergs/cm2. When adherent red cell-vesicle pairs were transferred into a Dextran-free buffer, the pair did not spontaneously separate.They maintained adhesive contact until forcibly parted, after which they would not read here. This demonstrates that Dextran forms a "cross-bridge" between the membrane surfaces. Red cell-vesicle aggregation was also tested in whole plasma, which normally yields affinity values in the range of 2-4 x 10-3 ergs/cm2 for red cell-red cell aggregation.However, no red cell-vesicle aggregation occurred in plasma, even for pure PC vesicles. This result indicates that either the aggregating plasma proteins (primarily fibrinogen) do not bind sufficiently to the lecithin surface, or they are shielded from binding to the surface by the presence of other nonaggregating components (perhaps albumin).