The common earthworm (Lumbricus terrestris) is being evaluated in our laboratories as a substitute for mice in metal toxicity studies. These two disparate species have enzymes in common, such as catalase, superoxide dismutase and glutathione-S-transferase. Also, worms respond similarly to these rodents for selenium and nickel toxicity. Worms are less sensitive, however, to metal toxicity. In this study earthworms were challenged with three different arsenic compounds: arsenite, arsenate and the vesicant phenyldichloroarsine (PDA). The median lethal dose for each arsenic compound was determined. The order of toxicity of the arsenic compounds to the worms was PDA > arsenite > arsenate (24 h LD50 values were 189.5, 191.0 and 519.4 mumol kg-1, respectively). Individual mammalian dithiol antidotes, namely the sodium salt of 2,3-dimercapto-1-propanesulfonic acid (DMPS), meso-dimercaptosuccinic acid (DMSA) or 2,3-dimercapto-1-propanol (BAL), were injected into the worms 5 min after various doses of the arsenic compound were administered. The decreases in acute toxicity values were recorded. All three antidotes protected the worms against arsenic toxicity with varying degrees of effectiveness. The protective action for the inorganic arsenic compounds was in the order DMPS > DMSA > BAL. For the organic arsenical, PDA, the most effective antidote was BAL.

Animals↗

PubMedDate not supplied

Cadmium-induced metallothionein in earthworms (Lumbricus terrestris).

Studies are continuing to compare the common earthworm (Lumbricus terrestris) to rodents by their reactions to toxic levels of metals. A recent study suggests that LD50 of selenium compounds were about ten times less in worms than in rodents, but the toxicity of cadmium was of the same order of magnitude between these diverse species. An interesting finding is that the common earthworm produces a Cd-bound protein, metallothionein, after the injection of cadmium salts, and, similar to rodents, two Cd-bound isoproteins can be isolated by a Sephacryl S-200 column and monitored by both atomic absorption and liquid scintillation spectroscopy.

Animals↗

PubMedDate not supplied

Can nutrition affect chemical toxicity?

Universally, the general population is exposed to a variety of "toxic" substances. Some of these are from manufactured goods and some from air and water pollution. Toxins are also normally found in many foods; however, unless the exposure is overwhelming, we are many times (even unknowingly) protected by the foods we eat. A judicious choice of food will counteract noxious agents. Therefore, the diet can be a major factor in determining who does and who does not show toxic symptoms following exposure. This review will cover three aspects. The first will be on protectors against metal toxicity. For example, whereas humans can consume fish that have absorbed mercury from contaminated bay water, selenium can act as a natural antagonist for mercury poisoning. (Naturally, too much selenium itself can be detrimental!) Some vegetables can accumulate cadmium from contaminated soil, and zinc from a variety of nuts is an antagonist of cadmium toxicity. Nitrites in preserved meats can be converted into nitroamines by saliva or mild stomach acid. Vitamin C found in oranges and bell peppers can inhibit that conversion. In addition, calcium antagonizes both lead and aluminum toxicity. The second aspect is on oxidants and antioxidants. Oxidative stress can lead to some cancers, atherosclerosis, and adverse effects of aging. Antioxidants are the best protectors of the damage caused by reactive oxygen species (ROS). The most effective antioxidants are found in highly colored fruits and vegetables such as carrots, tomatoes, and berries, called carotenoids. Flavonoids (polyphenols), another class of effective antioxidants that negate ROS, may or may not be colored. The third aspect is on gaps in current knowledge. Many foods naturally contain chemicals that are, in larger concentrations, quite toxic or carcinogenic. Biotransformations (detoxification mechanisms) involving type I and type II enzymes are known. Some foods do modify these enzymes either positively or negatively. Grapefruit contains a substance that inhibits an isoform of P450, making some cardiac drugs, as substrates, more toxic. There is inadequate information on what specific components are in a variety of foods that are associated with cancer prevention. The experimental carcinogenic compound (and suspected as a human carcinogen) found in overcooked, burnt, and fried meats and fish, namely IQ (2-amino-3-methyl-3H-imidazo[4,5f]quinoline, will be used as a prototype for what needs to be known about foods that will affect toxins.

Antioxidants↗

PubMedDate not supplied

The effects of the Gulf War in Israel--report from a rural family medical practice.

Throughout the 1991 Gulf War a rural Family Medicine practice in central Israel, situated 20 km from the nearest Scud missile attack area, continued to operate normally. During this period a reduction of more than 50% in clinic visits was recorded. The volume of requests for emergency care remained unchanged but elective hospital admissions decreased. Surprisingly, few new patients were diagnosed with anxiety states and no marked increase was registered in anxiolytic drug prescribing. Many patients, however, expressed feelings of deviance for not conforming with nationally sanctioned and endorsed anxiety levels. The decline in clinic visits noted was probably mediated through a temporary drop in practice accessibility due to the altered population mobility patterns caused by the war. During the 1991 Gulf War the Israeli population suffered not only the general stresses and strains of being in an active war zone but also the real tensions and anxieties associated with night-time attacks on the country by Iraqi Scud missiles. This article describes some of the ways which one rural family medicine practice in central Israel was affected by the dramatic if short-lived events of this war.

Anxiety↗

PubMedDate not supplied

Inactivity of two noble metals as carcinogens.

Silver and gold were evaluated for potential carcinogenicity by suspending fine (-300 mesh) powders in trioctanoin and injecting these intramuscularly in Fischer-344 rats. As a positive control, cadmium powder was tested; the vehicle alone served as the negative control. Under the conditions of these experiments, no tumors appeared at the site of injection in the silver-treated animals. Vehicle control (trioctanoin) and gold-treated groups each developed a single fibrosarcoma. In contrast, 60% of the cadmium-treated rats developed fibrosarcomas at the injection site. The mean survival time for the cadmium injected group was 16.5 months, whereas for all other groups it was approximately 23.5 months. It is concluded that the noble metals, silver and gold, are not carcinogenic under the conditions reported here.

Animals↗