Rhizosphere metabolism and its effect on phosphorus pools in the root zone of a submerged macrophyte, Isoëtes kirkii.

The presence of oxygen in lake sediments reduces sediment oxygen demand, and potentially improves sediment phosphorus retention and coupled nitrification/denitrification. However, the release of oxygen from the roots of macrophytes has not previously been measured in highly reducing sediments. Here, in the highly reducing environments of a commercial garden soil and sediment from a hyper-eutrophic lake, we used nine oxygen optodes, placed onto scintillation vials to detect oxygen in the rhizosphere of Isoetes kirkii referred to as quillworts. We calculated rhizosphere metabolism using "night-time regression" a method designed to estimate stream metabolism at the reach scale. After the incubations, sediment was collected from each vial (with and without macrophytes) and was subjected to sequential phosphorus extractions. A lag period between light availability and increasing oxygen concentration, that varied between individual optodes, was used to improve the accuracy of metabolism estimates as it was postulated to represent the distance between the root and the optode. Higher sediment oxygen demand in the lake sediment caused I. kirkii to have higher root oxygen release than those plants grown in the garden soil and may have pushed plants in lake sediment close to their ability to survive. This was evident as a significant, negative relationship between root oxygen release and increasing sediment oxygen demand, indicating that if photosynthesis decreased or sediment oxygen demand increased, the plants would no longer being able to oxygenate the sediment surrounding their roots, which would likely lead to death. Finally, the presence of quillworts in lake sediments significantly increased stores of metal oxide and recalcitrant phosphorus in the lake sediment but not the garden soil.

The potential impact of the use of homeopathic and herbal remedies on monitoring the safety of prescription products.

The purpose of this paper is to explore the possibility that adverse reactions and drug interactions arising from the use of homeopathic and herbal medicines could lead to confusion when adverse reactions to conventional medicines are reported. An extensive literature review was conducted on the occurrence of adverse reactions and drug interactions following the use of homeopathic or herbal remedies, and the potential for these to confound adverse event reporting to conventional medicines considered. The survey demonstrates the potential for herbal remedies and homeopathic products, to produce adverse drug reactions or drug interactions, and shows the scope for potential for confusion with those arising from conventional medicines. There is a need for greater awareness that adverse reactions apparently due to a conventional medicine, might in reality be due to a herbal medicine or a drug interaction between a herbal medicine and a conventional drug, particularly when a health professional is unaware of the extent of a patient's self-medication with alternative therapies.

Veterinary pharmacovigilance. Part 6. Predictability of adverse reactions in animals from laboratory toxicology studies.

Toxicological studies are conducted on constituents of veterinary medicinal products for a number of reasons. Aside from being a requirement of legislation, they are carried out for predictive purposes in the assessment of user safety or for the determination of consumer safety, for example, in the elaboration of maximum residue limits or tolerances. Alternatively, the results of toxicology studies may be available as they have been generated for registration of the drug for human medicinal purposes. This paper examines if the results of such studies have any predictive value for adverse reactions, which might occur during clinical use in animals. A number of adverse reactions, notably the Type A (toxicology or pharmacology dependent) should be predictable from these laboratory studies. However, as with human pharmaceutical products, they have less utility in predicting Type-B reactions (idiosyncratic in nature).

Purification of human dihydro-orotate dehydrogenase and its inhibition by A77 1726, the active metabolite of leflunomide.

Leflunomide is currently in phase-III clinical trials for the treatment of rheumatoid arthritis. In this study, we have focused our efforts on the study of the mechanism of action of the active metabolite of leflunomide, A77 1726, in cells and tissue of human origin. The human high-affinity binding protein for radiolabelled A77 1726 was purified from solubilized U937 membranes by following the binding activity through the purification process and was characterized as the mitochondrial enzyme dihydro-orotate dehydrogenase (DHO-DH). The human and murine enzyme displayed identical pI and molecular mass values on SDS/PAGE (43 kDa), which contrasts notably with previous reports suggesting a molecular mass of 50 kDa for the human enzyme. DHO-DH activity was inhibited by A77 1726 and its analogue HR325 with similar potency in U937 and human spleen membrane preparations. HR325 was found to be anti-proliferative for phytohaemagglutinin-stimulated human peripheral blood mononuclear cells, at the same concentrations that caused accumulation of DHO and depletion of uridine. Supplementation of the cultures with exogenous uridine led to partial abrogation of the anti-proliferative effect. This is in line with our recent demonstration that the anti-proliferative effect in vitro of A77 1726 on lipopolysaccharide-stimulated mouse spleen cells was mediated by DHO-DH inhibition [Williamson, Yea, Robson, Curnock, Gadher, Hambleton, Woodward, Bruneau, Hambleton, Moss et al., (1995) J. Biol. Chem. 270, 22467-22472]. Thus, DHO-DH inhibition by A77 1726 and its analogues is responsible for the anti-proliferative effects in vitro of the compounds on human cells and is likely to be responsible for some of its effects in vivo.

Hyperthermia in cancer treatment: current and future prospects.

The renewed interest in the possible use of localized hyperthermia in cancer therapy is prompted by two major realizations. The first is the radiobiological evidence indicating that there may be a significant advantage in the use of heat alone or combined with radiation therapy or chemotherapy to enhance the inactivation of tumor cells The second is that early clinical investigation with refractory malignant tumors at temperatures between 41 degrees C and 45 degrees C have shown tumor regression response rate over 70% without increasing normal tissue complication. A phase I/II study using electromagnetic hyperthermia immediately following administration of ionizing radiation was begun at Duke in the fall of 1976 to evaluate the response of normal tissues, the regression of cutaneous and subcutaneous tumors, and the feasibility of such combined modalities in therapeutic radiology. Each hyperthermia session consisted of 45 minutes at 42-43.5 degrees C 2-3 times per week immediately following radiotherapy. The radiation therapy fraction size was usually 2-3 Gy 3-5 times per week with a maximum total of 48 Gy. The 60+ patients treated to date have had squamous cell carcinoma, adenocarcinoma, malignant melanoma, plasmacytoma, liposarcoma, epithelioid sarcoma, and undifferentiated carcinoma. After more than 600 hyperthermia sessions, we have found: (1) local hyperthermia with microwave alone or in combination with ionizing radiation can be used with excellent normal tissue tolerance provided local tissue temperatures are carefully monitored and controlled; (2) a significantly higher level of preferential heat induction into tumor tissue is possible as compared to surrounding normal tissues; (3) repeated hyperthermia at 42-43.5 degrees C for 45 minutes per session immediately following radiation therapy yields favorable therapeutic results. Tumor regression response rate of over 70% was achieved without concomitant increase of normal tissue complication. Therefore, the potentially significant impact on clinical cancer therapy, whether of curative or palliative intent, by moderate thermotherapy is evident. Technical advances to optimize such treatment methods including R & D for delivering a known localized quantity of heat to tumors in any location in the body are expected to progress rapidly. The methods with most promising potential for inducing local thermotherapy are those involving the use of electromagnetic waves, e.g., radiofrequency energy, microwave energy, and ultrasound energy.