Antinociceptive effect of systemically administered dipyrone (metamizol), magnesium chloride or both in a murine model of cancer.

BACKGROUND: Opioid effectiveness to treat cancer pain is often compromised by the development of tolerance and the occurrence of undesirable side effects, particularly during long-term treatment. Hence, the search for more efficient analgesics remains a necessity. The main goal of this study was to relieve neuropathic symptoms associated with tumour growth by administering the non-opioid analgesic dipyrone (DIP) alone or in combination with magnesium chloride (MgCl2 ), an adjuvant that blocks the NMDA receptor channel. METHODS: Mice were inoculated with a melanoma cell line (B16-BL6) in the left thigh and two protocols were used to evaluate the effect of DIP (270 mg/kg), MgCl2 (200 mg/kg), or the combination DIP-MgCl2 . In the therapeutic protocol the drugs, alone or combined, were administered once tumour had promoted increased nociception. In the preventive protocol, drugs were administered prior to the appearance of the primary tumour. Tumour growth was assessed with a caliper and nociception was determined using behavioural tests. RESULTS: DIP promoted antinociception only at the beginning of both protocols due to the development of tolerance. The combination DIP-MgCl2 improved the antinociceptive effect, avoiding tolerance and reducing tumour growth in the preventive treatment, more efficiently than each compound alone. CONCLUSIONS: These results suggest that DIP-MgCl2 may represent a safe, affordable and accessible option to reduce tumour growth and to treat cancer pain avoiding the risk of tolerance, without the typical complications of opioids agents, particularly when long-term treatment is required. SIGNIFICANCE: This study shows a non-opioid analgesic combined with an adjuvant as a therapeutic option to treat cancer pain. The avoidance of antinociceptive tolerance when repeated administration is required, as well as tumor growth reduction, are additional advantages to be considered.

Carboxylate metabolism in sugar beet plants grown with excess Zn.

The effects of Zn excess on carboxylate metabolism were investigated in sugar beet (Beta vulgaris L.) plants grown hydroponically in a growth chamber. Root extracts of plants grown with 50 or 100µM Zn in the nutrient solution showed increases in several enzymatic activities related to organic acid metabolism, including citrate synthase and phosphoenolpyruvate carboxylase, when compared to activities in control root extracts. Root citric and malic acid concentrations increased in plants grown with 100µM Zn, but not in plants grown with 50µM Zn. In the xylem sap, plants grown with 50 and 100µM Zn showed increases in the concentrations of citrate and malate compared to the controls. Leaves of plants grown with 50 or 100µM Zn showed increases in the concentrations of citric and malic acid and in the activities of citrate synthase and fumarase. Leaf isocitrate dehydrogenase increased only in plants grown with 50µM Zn when compared to the controls. In plants grown with 300µM Zn, the only enzyme showing activity increases in root extracts was citrate synthase, whereas the activities of other enzymes decreased compared to the controls, and root citrate concentrations increased. In the 300µM Zn-grown plants, the xylem concentrations of citric and malic acids were higher than those of controls, whereas in leaf extracts the activity of fumarase increased markedly, and the leaf citric acid concentration was higher than in the controls. Based on our data, a metabolic model of the carboxylate metabolism in sugar beet plants grown under Zn excess is proposed.

Effects of zinc toxicity on sugar beet (Beta vulgaris L.) plants grown in hydroponics.

The effects of high Zn concentration were investigated in sugar beet (Beta vulgaris L.) plants grown in a controlled environment in hydroponics. High concentrations of Zn sulphate in the nutrient solution (50, 100 and 300 microm) decreased root and shoot fresh and dry mass, and increased root/shoot ratios, when compared to control conditions (1.2 microm Zn). Plants grown with excess Zn had inward-rolled leaf edges and a damaged and brownish root system, with short lateral roots. High Zn decreased N, Mg, K and Mn concentrations in all plant parts, whereas P and Ca concentrations increased, but only in shoots. Leaves of plants treated with 50 and 100 microm Zn developed symptoms of Fe deficiency, including decreases in Fe, chlorophyll and carotenoid concentrations, increases in carotenoid/chlorophyll and chlorophyll a/b ratios and de-epoxidation of violaxanthin cycle pigments. Plants grown with 300 microm Zn had decreased photosystem II efficiency and further growth decreases but did not have leaf Fe deficiency symptoms. Leaf Zn concentrations of plants grown with excess Zn were high but fairly constant (230-260 microg.g(-1) dry weight), whereas total Zn uptake per plant decreased markedly with high Zn supply. These data indicate that sugar beet could be a good model to investigate Zn homeostasis mechanisms in plants, but is not an efficient species for Zn phytoremediation.

AZT treatment induces molecular and ultrastructural oxidative damage to muscle mitochondria. Prevention by antioxidant vitamins.

AIDS patients who receive zidovudine (AZT) frequently suffer from myopathy. This has been attributed to mitochondrial (mt) damage, and specifically to the loss of mtDNA. This study examines whether AZT causes oxidative damage to DNA in patients and to skeletal muscle mitochondria in mice, and whether this damage may be prevented by supranutritional doses of antioxidant vitamins. Asymptomatic HIV-infected patients treated with AZT have a higher urinary excretion (355+/-100 pmol/kg/d) of 8-oxo-7, 8-dihydro-2'-deoxyguanosine (8-oxo-dG) (a marker of oxidative damage to DNA) than untreated controls (asymptomatic HIV-infected patients) (182+/-29 pmol/kg/d). This was prevented (110+/-79 pmol/kg/d) by simultaneous oral treatment with AZT plus antioxidant vitamins (C and E). Mice treated with AZT also had a significantly higher urinary excretion of 8-oxo-dG than controls. Skeletal muscle mtDNA of mice treated with AZT had more 8-oxo-dG than controls. mt lipoperoxidation was also increased and skeletal muscle glutathione was oxidized. These effects may be due to an increased peroxide production by muscle mitochondria of AZT-treated animals. Dietary supplements with vitamins C and E at supranutritional doses protect against oxidative damage to skeletal muscle mitochondria caused by AZT.

A Ginkgo biloba extract (EGb 761) prevents mitochondrial aging by protecting against oxidative stress.

The effect of aging on indices of oxidative damage in rat mitochondria and the protective effect of the Ginkgo biloba extract EGb 761 was investigated. Mitochondrial DNA from brain and liver of old rats exhibited oxidative damage that is significantly higher than that from young rats. Mitochondrial glutathione is also more oxidized in old than in young rats. Peroxide formation in mitochondria from old animals was higher than in those from young ones. According to morphological parameters (size and complexity), there are two populations of mitochondria. One is composed of large, highly complex mitochondria, and the other population is smaller and less complex. Brain and liver from old animals had a higher proportion of the large, highly complex mitochondria than seen in organs from young animals. Treatment with the Ginkgo biloba extract EGb 761 partially prevented these morphological changes as well as the indices of oxidative damage observed in brain and liver mitochondria from old animals.