Lethal and sub-lethal effects of chlorination on green mussel Perna viridis in the context of biofouling control in a power plant cooling water system.

Continuous chlorination is a widely followed cooling water treatment practice used in the power industry to combat biofouling. The green mussel Perna viridis is one of the dominant fouling organisms ( > 70%) in the Madras Atomic Power Station. Mortality pattern as well as physiological responses such as oxygen consumption, filtration rate, byssus thread production and faecal matter production of three different size groups of this mussel were studied at different chlorination concentrations. At 0.7 mg l(-1) residual chlorine, 3-4 cm size mussels showed 100% mortality in 553.3 h while 8-9 cm size group mussels died within 588 h. At a relatively high level of residual chlorine (9.1 mg l(-1)), 100% mortality in 3-4 cm and 8-9 cm size groups took 94 and 114 h, respectively. All physiological activities studied showed a progressive reduction as chlorine residuals were increased from 0 to 0.55 mg l(-1). The data indicated that the green mussel can sense a residual chlorine level as low as < 0.15 mg l(-1) and complete valve closure occurs only at 0.55 mg l(-1). The paper also shows that the sub-lethal physiological responses are better indices than lethal responses in planning chlorination strategies.

Influence of temperature on the physiological responses of the bivalve Brachidontes striatulus and its significance in fouling control.

Heat treatment offers an alternative method of fouling control to chlorination in power plants. In order to optimise such a procedure it is important to understand the responses of fouling organisms to elevated water temperatures. In this paper we report results of experiments on the lethal and sub-lethal effects of temperature on the bivalve Brachidontes striatulus which is one of the major foulants in the process seawater heat exchangers of Madras Atomic Power Station located at Kalpakkam, on the east coast of India. The important physiological activities, such as, oxygen consumption, filtration rate, byssus thread production and faecal matter production were studied at temperatures varying from 20 to 38 degrees C. Three different size groups [3-5 mm shell length (group 1), 6-10 mm (group 2), 11-15 mm (group 3)] of B. striatulus were used for the experiments. The results showed physiological activities were maximum at 35 degrees C, minimum at 20 and 38 degrees C. Physiological activities increased with size except for byssus thread production, which did not show any trend. Survival times showed a reduction from 30 h at 39 degrees C to < 1 h at 45 degrees C and were independent of body size.

International perceptions and approval of gene therapy.

Gene therapy is in clinical trials in a number of countries, raising the question of whether different ethical standards can be justified in different countries. One key issue is how divergent are the perceptions and bioethical reasoning of peoples around the world. An International Bioethics Survey with 150 questions, including 35 open ones, was developed to look at how people think about diseases, life, nature, and selected issues of science and technology, biotechnology, genetic engineering, genetic screening, and gene therapy. The mail response survey was conducted in 1993 among the public in Australia, India, Israel, Japan, New Zealand, Russia, and Thailand, and the same written survey was conducted among university students in Australia, Hong Kong, India, Japan, New Zealand, The Philippines, Russia, Singapore, and Thailand. Similar questions were included in an international high school education bioethics survey among high school teachers in Australia, Japan, and New Zealand. Further international comparisons to the United States and Europe are made. About three-quarters of all samples supported personal use of gene therapy, with higher support for children's use of gene therapy. The diversity of views was generally similar within each country. The major reasons given were to save life and increase the quality of life. About 5-7% rejected gene therapy, considering it to be playing God, or unnatural. There was very little concern about eugenics (0.5-2%), and more respondents gave supportive reasons like "improving genes," especially in Thailand and India. Support for specific applications was significantly less for "improving physical characters," "improving intelligence," or "making people more ethical" than for curing diseases like cancer or diabetes, but there was little difference between inheritable or noninheritable gene therapy.

Trihalomethane levels in Madras public drinking water supply system and its impact on public health.

It is known that trihalomethanes (THM) are formed during chlorination of drinking water for disinfection. Heightened concern about these substances is due to the fact that THMs are now characterized as potential mutagen, carcinogen and teratogen. Thus, it is a risk factor in human beings. In the present study, a total number of 13 stations located in different drinking water trunk mains of the city of Madras were analysed for THM using the Gas Liquid Chromatographic method. It is reported that THM are formed after treatment of raw water with chlorine at the levels required for disinfection. The THM level in drinking water increased towards the dead-end of the water trunk mains. A relationship between the distance travelled by the potable water and the level of THM was established. At certain stations, the total trihalomethanes level (TTHM) was found to exceed the EPA's maximum contaminant level. Further, an intermittent addition of the precursors for the formation of THM through the seepage of polluted River Cooum water into the pipe lines has been demonstrated. An experiment on the trihalomethane formation potential (THMFP) clearly revealed the occurrence of higher magnitude of humic substances in source water. Therefore, it is suggested that if suitable steps are not taken, various environmental factors may trigger the THM kinetics. Hence, it is obvious that pretreatment regulations proposed by developed countries are essential if safe drinking water is to be supplied to the people of Madras.

Studies on metachromasia. III. Toluidine blue-substrate interaction and metachromasia.

With salts as substrates the metachromatic responses of the thiazine dye, Toluidine blue are studied. It is found that generally salts produce a gamma-metachromatic response. The substrate-dye interaction is studied in detail and the results are discussed in the light of various interpretations of previous workers. It is suggested that toluidine blue may have two sites that are responsible for the exhibition of green and red metachromatic responses. The influence of water on metachromasia has been studied and is reported to bring about an oscillation of spectral colours. Spectrophotometric studies were also carried out.

Influence of carbonates and other salts in tissues on the Schiff's reagent.

Application of the Schiff's reagent on fresh and undecalcified cuticle of crustaceans such as Emerita asiatica and Ocypoda platytarsis showed positive results with their calcified layer which led to suggest that salts of calcium account for the staining. In vitro studies with carbonate and other salts furnished confirmatory evidence. It is suggested that in tests involving the Schiff's reagent proper removal of resident salts must be carried out.

An optimum pH for the demonstration of chitin in Periplanata americana using Lugol's iodine.

Modification of chitosan test of Campbell is suggested with a controlled procedure involving heating with saturated potassium hydroxide at 160 degrees C for a period of 45 min and subsequent washing of the deacetylated chitin in running water and application of Lugol's iodine solution (1:2:300, w/w/v) at a pH range of 1.4 to 4.0, thus replacing the use of dilute sulphuric acid. Consistent results were obtained not only with the cuticle of Periplanata americana but also with the cuticle of Emerita asiatica (crustacea).