scholarly journals Hormonal Effect on Cultivated Insect Tissues : V. The Role of Testis Proteins in Spermiogenesis of the Cabbage Armyworm, Mamestra brassicae, in vitro (Lepidoptera : Noctuidae)

1982 ◽  
Vol 17 (3) ◽  
pp. 385-392 ◽  
Author(s):  
Toshiaki SHIMIZU ◽  
Shigemi YAGI
Keyword(s):  
Mamestra Brassicae ◽  
Hormonal Effect ◽  
Lepidoptera Noctuidae

scholarly journals Role of Proteolysis in Determining Potency ofBacillus thuringiensis Cry1Ac δ-Endotoxin

2000 ◽  
Vol 66 (12) ◽  
pp. 5174-5181 ◽  
Author(s):  
Daniel J. Lightwood ◽  
David J. Ellar ◽  
Paul Jarrett
Keyword(s):  
Membrane Vesicles ◽  
Apparent Molecular Weight ◽  
Pieris Brassicae ◽  
Proteolytic Processing ◽  
Mamestra Brassicae ◽  
Ofbacillus Thuringiensis ◽  
Domain I

ABSTRACT Bacillus thuringiensis protein δ-endotoxins are toxic to a variety of different insect species. Larvicidal potency depends on the completion of a number of steps in the mode of action of the toxin. Here, we investigated the role of proteolytic processing in determining the potency of the B. thuringiensis Cry1Ac δ-endotoxin towards Pieris brassicae (family: Pieridae) andMamestra brassicae (family: Noctuidae). In bioassays, Cry1Ac was over 2,000 times more active against P. brassicae than against M. brassicae larvae. Using gut juice purified from both insects, we processed Cry1Ac to soluble forms that had the same N terminus and the same apparent molecular weight. However, extended proteolysis of Cry1Ac in vitro with proteases from both insects resulted in the formation of an insoluble aggregate. With proteases from P. brassicae, the Cry1Ac-susceptible insect, Cry1Ac was processed to an insoluble product with a molecular mass of ∼56 kDa, whereas proteases from M. brassicae, the non-susceptible insect, generated products with molecular masses of ∼58, ∼40, and ∼20 kDa. N-terminal sequencing of the insoluble products revealed that both insects cleaved Cry1Ac within domain I, butM. brassicae proteases also cleaved the toxin at Arg423 in domain II. A similar pattern of processing was observed in vivo. When Arg423 was replaced with Gln or Ser, the resulting mutant toxins resisted degradation by M. brassicae proteases. However, this mutation had little effect on toxicity to M. brassicae. Differential processing of membrane-bound Cry1Ac was also observed in qualitative binding experiments performed with brush border membrane vesicles from the two insects and in midguts isolated from toxin-treated insects.

The role of silicon in forages: A quantitative X-Ray study

1987 ◽  
Vol 45 ◽  
pp. 416-417
Author(s):  
Janet H. Woodward ◽  
D. E. Akin
Keyword(s):  
Sodium Acetate ◽  
Dry Matter ◽  
Acetate Buffer ◽  
Plant Tissues ◽  
Sodium Acetate Buffer ◽  
X Ray ◽  
Dry Matter Digestibility ◽  
Percent Composition

Silicon (Si) is distributed throughout plant tissues, but its role in forages has not been clarified. Although Si has been suggested as an antiquality factor which limits the digestibility of structural carbohydrates, other research indicates that its presence in plants does not affect digestibility. We employed x-ray microanalysis to evaluate Si as an antiquality factor at specific sites of two cultivars of bermuda grass (Cynodon dactvlon (L.) Pers.). “Coastal” and “Tifton-78” were chosen for this study because previous work in our lab has shown that, although these two grasses are similar ultrastructurally, they differ in in vitro dry matter digestibility and in percent composition of Si.Two millimeter leaf sections of Tifton-7 8 (Tift-7 8) and Coastal (CBG) were incubated for 72 hr in 2.5% (w/v) cellulase in 0.05 M sodium acetate buffer, pH 5.0. For controls, sections were incubated in the sodium acetate buffer or were not treated.

An integrated screening method for evaluating the pulmonary toxicity of inhaled particulates: Role of microscopic techniques in assessing pulmonary macrophage clearance functions

1990 ◽  
Vol 48 (3) ◽  
pp. 826-827
Author(s):  
David B. Warheit ◽  
Lena Achinko ◽  
Mark A. Hartsky
Keyword(s):  
Bronchoalveolar Lavage ◽  
Pulmonary Toxicity ◽  
Screening Method ◽  
Pulmonary Response ◽  
Inhaled Particles ◽  
Cytochemical Analysis ◽  
Pulmonary Macrophages ◽  
Integrated Screening

There is a great need for the development of a rapid and reliable bioassay to evaluate the pulmonary toxicity of inhaled particles. A number of methods have been proposed, including lung clearance studies, bronchoalveolar lavage analysis, and in vitro cytotoxicity tests. These methods are often limited in scope inasmuch as they measure only one dimension of the pulmonary response to inhaled, instilled or incubated dusts. Accordingly, a comprehensive approach to lung toxicity studies has been developed.To validate the method, rats were exposed for 6 hours or 3 days to various concentrations of either aerosolized alpha quartz silica (Si) or carbonyl iron (CI) particles. Cells and fluids from groups of sham and dust-exposed animals were recovered by bronchoalveolar lavage (BAL). Alkaline phosphatase, LDH and protein values were measured in BAL fluids at several time points postexposure. Cells were counted and evaluated for viability, as well as differential and cytochemical analysis. In addition, pulmonary macrophages (PM) were cultured and studied for morphology, chemotaxis, and phagocytosis by scanning electron microscopy.

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