7 November, 1996

Journal- November 7, 1996

This morning I helped Gamini with a cytotoxicity assay. We are looking for chemicals that have the ability to inhibit cell growth. One use for cytotoxic compounds is in the treatment of cancer. A person who is undergoing chemotherapy is using drugs that interfere with the reproduction of cancerous cells.

To perform the assay, a gravid urchin is injected with potassium chloride to stimulate spawning. Within a few minutes either eggs or sperm will be released and is collected in a beaker. The urchin in the photo is a female and a stream of thousands of eggs is being released. The sperm and eggs are combined in a solution that contains the compound being assayed. If the compound is not cytotoxic, fertilized will occur and a membrane will appear around the egg.

After the divers collect sponges, Jim will catalogue and freeze dry all the samples. It's usually up to Gamini to extract the compounds from the freeze-dried samples. He then gives the extract to me for a microbial assay. The assays I perform are designed to determine if the compound will inhibit either fungal or microbial growth. We have several indicator microbes and will include others specific to the local environment as Chuck isolates them. If the results are positive the extract goes back to Gamini or Bill for further purification until the specific compound that caused the bioactivity is determined. Of the natural products that have been identified, only about 1% are used pharmacologically. Of the sponges we have collected only about 10% have products that are identified to be microbially active. It seems like the odds of finding something are slim but the potential rewards are high.

Dom Tedeschi


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