Brown recluse spider envenomation: a prospective trial of hyperbaric oxygen therapy

OBJECTIVES

Loxosceles reclusa (brown recluse) spider bites can produce severe skin lesions that may necessitate extensive surgical repair. This study delineated the effects of hyperbaric oxygen (HBO) therapy on these lesions by performing a prospective controlled animal study.

METHODS

After approval by the Institutional Animal Care and Use Committee, 41 New Zealand white rabbits received 64 intradermal injections of 73 microL of raw venom extract mixed with physiologic buffered saline (Dulbecco's solution). Control injections were made with buffer. The animals were divided into 5 groups: 1) venom and no HBO; 2) venom and 1 immediate HBO treatment (100% O2); 3) venom and immediate HBO with 10 treatments (100% O2); 4) venom and then delayed (48 hr) HBO therapy with 10 treatments (100% O2); and 5) venom and immediate hyperbaric treatment with normal inspired PO2 for 10 treatments (8.4% O2). Three animals in group 2 also received a control sodium citrate buffer injection. HBO treatments were at 2.5 atm absolute (ATA) for 90 minutes twice daily. Daily measurements were made of the lesion diameter, and skin blood flow using a laser Doppler probe.

RESULTS

There was no significant effect of HBO on blood flow at the wound center or 1-2 cm from the wound center. Standard HBO significantly decreased wound diameter at 10 days (p < 0.0001; ANOVA), whereas hyperbaric treatment with normoxic gas had no effect. Histologic preparations from 2 animals in each group revealed that there were more polymorphonuclear leukocytes in the dermis of all the HBO-treated animals when compared with the venom-alone and sodium-citrate controls.

CONCLUSION

HBO treatment within 48 hours of a simulated bite from L. reclusa reduces skin necrosis and results in a significantly smaller wound in this model. The mechanism appears unrelated to augmented local blood flow between treatments.

Glutathione depletion increases the cytotoxicity of melphalan to PC-3, an androgen-insensitive prostate cancer cell line

Prostate cancer that is androgen-insensitive is unresponsive to a wide spectrum of cytotoxic agents, including all of the alkylating agents. Since a major pathway for the detoxification of the alkylating agents is conjugation with glutathione (GSH), GSH depletion has proved to be effective as a technique to restore melphalan sensitivity in melphalan-resistant cancer cell lines. However, the effect of GSH depletion has not been widely studied in tumor cell lines that have not developed resistance due to previous exposure to alkylating agents. Thus, we decided to investigate GSH depletion as a technique to increase melphalan cytotoxicity to PC-3 cells, an androgen-insensitive prostate cancer line. After 2 and 6 h incubation with 0.25-5 microM melphalan, virtually no effect was observed on either clonogenic lethality or MTT viability until 5 microM exposures. A 24-h incubation of the cells with 100 microM buthionine sulfoximine (BSO), an inhibitor of GSH synthesis, reduced the GSH content by 70%-75%. Following GSH depletion, an increase in clonogenic lethality and a decrease in MTT viability occurred after exposure to concentrations as low as 0.25 microM. The dose modification factor ranged from 2.9 after 2 h incubation to 4.5 at 6 h. These results provide support for additional studies in prostate cancer for further investigation of GSH depletion as a technique to induce sensitivity to alkylating agents in this chemotherapy-resistant tumor.

Three cases of human bladder cancer following high dose cyclamate ingestion

Vesical implantation and oral feeding studies in animals raised sufficient suspicion of the carcinogenic propensity of cyclamates to result in their withdrawal from sale throughout the world. The structural similarity to known carcinogens, an effect on human chromosomes in tissue culture and a high carcinogenic potential when combined with non-injurious co-carcinogens gave further support to this ban. On the other hand, numerous epidemiological studies failed to support any statistical relationship between cyclamate ingestion and vesical carcinoma in man. Three patients are described in whom vesical carcinoma developed after a prolonged period of ingestion of an unusually high amount of cyclamate sweetener. Moreover, the severity of the disease appeared to be proportional to the dose ingested. Although this is not a conclusive indictment of the role of cyclamates we believe that patients with bladder cancer should be questioned about intake of cyclamates either directly or in diet soft drinks.