A simple method for assaying the activity of adsorbed tetanus toxoids

The authors have developed a simplified activity test for Tetanus Toxoids Adsorbed, based on the comparison of antitoxin levels in mice 4 weeks after injection of a reference toxoid and of the vaccine to be tested. Titration of tetanus antitoxin is achieved by passive agglutination of turkey RBC sensitized by means of glutaraldehyde. After preliminary experiments establishing feasibility of this method, the authors have obtained reproducible and quantitative results. They observed an increase of the immune response by a booster and an immunostimulation when pertussis component is present. They have found close correlation in immunized mice between the titre of circulating antibodies and the survival/death response after challenge by tetanus toxin as done in the official control. This simplified method using a reduced number of animals, yields, nevertheless, quantified results with confidence limits. Thus it is suitable for laying down a norm and can in many cases take the place of the official potency test which is tedious, expensive and often criticized.     

A novel and simple method of screening compounds for interaction with DNA: A validation study

We report the development of a simple, cost-effective assay for detecting compounds that have the ability to interact with and modify DNA. Potential uses for the assay lie in the areas of early genotoxicity testing of drug candidates, anticancer and antibiotic drug discovery, environmental monitoring and testing in the food, beverage and cosmetics industries. At present the assay has been used to assess direct-acting compounds only and it is yet to be established whether the assay is compatible with bio-activation. The methodology is based on the oxidative reaction of potassium permanganate with pyrimidine bases, which have become perturbed and more reactive by the agent under test. Results are recorded by use of UV/vis spectroscopy. The adaptation to a multi-well plate format provides the capacity for high throughput utilizing small amounts of compounds. Over 100 compounds, comprising different classes of DNA-binding chemicals as well as non-binding controls, have been put through the assay and the results compared with existing genotoxicity testing data from other methods. The assay has shown to be predictive of the results of other genotoxicity testing methods. We have found that the method is overall predictive of 71% of Ames bacterial reverse-mutation test results (where data are given) encompassing both negative and positive results.     

A simple method for screening antimicrobial compounds with application to plant disease and fruit quality

Aims:  It is often difficult to extrapolate information from a Petri dish and apply it to commercial applications as with antimicrobial assays. Often large volumes of commodities are used for a virtually untested protocol and result in an unnecessary expenditure of time and materials. An intermediate method, where experimental compounds could be tested directly on a specific commodity without expending large quantities of either sample or compound, would be practical and economical.
Methods and Results:  A method was developed that employs the use of a small experimental chamber in which pieces of natural materials (e.g. fruit) can be tested with antimicrobial compounds. This method uses a type of autoclavable incubation chamber with a filter paper base, hydrating sponge pieces and a sterile glass sample platform. The chamber offers a sterile, controlled environment and can be manipulated to serve a number of studies.
Conclusion:  The chamber results are more analogous to what happens on whole fruit than the Petri dish.
Significance and Impact of the Study:  This method is presently used to screen for antimicrobial compounds and treatments needed to control serious economic pests compromising Florida's agriculture.     

Morphogenetic effects of some volatile,organic compounds on Pestalotia rhododendri

Summary Some volatile alcohols, acids, esters, aldehydes and ketones influenced the morphogenesis of Pestalotia rhododendri when added through the gas phase. Linear growth, formation of aerial hyphae and production of conidial spores were determined. Mostly, increasing amounts of test substance inhibited linear growth and only one case of stimulation was noticed, viz. by nonenal.Many substances stimulated formation of aerial hyphae, particularly allyl alcohol, acetaldehyde and nonanal, but inhibitions were more common.Spore production was promoted by compounds from all the chemical classes investigated. The activity decreased as follows; alcohols > esters > acids, aldehydes > ketones. Inhibitions of spore production were also observed.The effects were reproducible on two different media. Pestalotia sydowiana exhibited the same main responses as the other Pestalotia species, but only two substances, furfural and n-propanol, were observed to promote spore formation of this species.     

A novel non-contact bioassay method for quantitative evaluation of vapour phase toxicity of insecticides against mosquitoes

The recent advancement in new generation fluorinated pyrethroids (e.g., transfluthrin, metofluthrin etc.), the use of semi-volatile vapour phase insecticides for control of mosquitoes and other domestic pests rises. Enabling the examination of the vapour toxicity profiles of these molecules and many other similar new generation molecules will provide new avenues for researchers for understanding the bio-potency in the spatial killing of pests. Hence, it is critical to establish a well-controlled portable vapour-phase bioassay method that can provide the desired precision, accuracy, linearity and robustness. In this respect, we have designed a vapour-toxicity apparatus comprising glass assemblies and developed a novel bioassay method. We found that KT₅₀ and percentage knockdown at 60?min reflect the concentration dependency. This validates and confirms that the method is sensitive enough to distinguish between concentrations and suitable for concentration-response experiments. We found that KT₅₀ and percentage knockdown at 60?min at a given concentration does not differ significantly between experiments. Hence, the method has repeatability and precision. Percentage mortality and total KT₅₀ against Culex quinquefasciatus shows that percentage mortality increases and KT₅₀ decreases linearly with the increasing concentration. This method provides an easy to operate tool to test the vapour toxicity profiles of any vapour phase insecticide molecules against mosquitoes and flying insects.     

A novel method for characterisation of microbial growth kinetics on volatile organic compounds

A novel method for the determination of microbial growth kinetics on hydrophobic volatile organic compounds (VOC) has been developed. A stirred tank reactor was operated as a fed-batch system to which the VOC was continuously fed via the gas phase, assuring a constant VOC concentration in the mineral medium. A flow of air was saturated with the VOC, and then mixed with a further flow of air, to obtain a predetermined VOC concentration. Thus, different VOC concentrations in the mineral medium could be obtained by altering the VOC concentration in the feed gas. The growth kinetics of Xanthobacter autotrophicus GJ10 on 1,2-dichloroethane (DCE) and of Pseudomonas sp. strain JS150 on MonoChloroBenzene (MCB) were assessed using this method. The growth of strain JS150 was strongly inhibited at MCB concentrations higher than 160 mg l⁻¹, and the results were fitted using a piecewise function. The growth kinetics of strain GJ10 were described by the Luong model where maximum growth rate μ_max = 0.12 h⁻¹, substrate saturation constant K _S = 7.8 mg l⁻¹, and maximum substrate concentration S _m (above which growth is completely inhibited) = 1080 mg l⁻¹. Varying nitrogen and oxygen flows enabled the effect of oxygen concentration on the growth kinetics of Pseudomonas JS150 to be determined. Received: 30 November 1998 / Received revision: 19 March 1999 / Accepted: 20 March 1999     

A new,sensitive and simple bioluminescence test for mutagenic compounds

A spontaneous dark variant of the luminous bacterium Photobacterium leiognathi was isolated. The reversion frequency of this variant to genetic-hereditary luminescent cells is greatly increased by nanogram quantities of different base-substitution and frameshift agents. This makes it possible to detect mutagenic compounds at concentrations 100 times lower than that detected by the Ames Test. Curing agents, such as acridine dyes, ethidium bromide and sodium dodecyl sulfate, are also very active in the reversion of this dark variant to the luminous state, but fail to revert it to a genetic-hereditary luminescent type. The nature of the primary mutation in the dark variant, and the potential use of this luminescence system for detecting different classes of carcinogenic chemical, are discussed.     

菜粉蝶幼虫、蛹和成虫的雌雄形态鉴别

利用体视显微镜观察、测量、记录菜粉蝶不同虫态雌雄个体间的形态特征差异。雌雄菜粉蝶幼虫、蛹和成虫均存在显著的雌雄二型特征,3龄之后雄性幼虫的第6腹节有一对肾型黑斑,雌性幼虫无此斑。雄蛹第9腹节有生殖孔和一条短纵裂缝,裂缝两侧有凹凸不平的半圆形瘤状突起;雌蛹腹部第8、9腹节分别有生殖孔和产卵孔,且两孔之间亦有一条纵裂缝。雌蝶前翅背面有一对上下排列的黑圆斑,其腹部末端外生殖器为圆筒型;雄蝶前翅背面一对黑斑相对较小,颜色较浅,尤其下斑为浅灰色,腹部末端具钳状外生殖器。本研究揭示了菜粉蝶幼虫、蛹及成虫不同虫态的雌雄二型差异,比较研究并提出了便于快速鉴别雌雄个体的典型特征和识别方法。     

A simple and convenient biochemical method for sex identification in the marine mussel,Mytilus edulis L.

One of two chromophores is formed on heating the mantle tissue of Mytilus edulis with thiobarbituric acid (TBA). Application of the test to male mussels yields a strong yellow colour (λ_max453 and 490 nm), whereas in females, a pink colour (λ_max532 nm) develops. While the latter is characteristic of the products of lipid peroxidation, it appears that the yellow colour may be derived from the 2-deoxyribose moiety of DNA. The TBA reaction can be used for the rapid, accurate sex identification in Mytilus edulis over 9–10 months of the year.