Resistance to levamisole resolved at the single-channel level.
Levamisole is commonly used to treat nematode parasite infections but therapy is limited by resistance. The purpose of this study was to determine the mechanism of resistance to this selective nicotinic drug. Levamisole receptor channel currents in muscle patches from levamisole-sensitive and levamisole-resistant isolates of the parasitic nematode Oesophagostomum dentatum were compared. The number of channels present in patches of sensitive and resistant isolates was similar at 10 microM levamisole, but at 30 microM and 100 microM the resistant isolate contained fewer active patches, suggesting desensitization. Mean Po and open times were reduced in resistant isolates. The distribution of conductances of channels in the sensitive isolate revealed a heterogeneous receptor population and the presence of G25, G35, G40, and G45 subtypes. A G35 subtype was missing in the resistant isolate. Resistance to levamisole was produced by changes in the averaged properties of the levamisole receptor population, with some receptors from sensitive and resistant isolates having indistinguishable characteristics. (+info)
One GABA and two acetylcholine receptors function at the C. elegans neuromuscular junction.
We describe an electrophysiological preparation of the neuromuscular junction of the nematode C. elegans, which adds to its considerable genetic and genomic resources. Mutant analysis, pharmacology and patch-clamp recording showed that the body wall muscles of wild-type animals expressed a GABA receptor and two acetylcholine receptors. The muscle GABA response was abolished in animals lacking the GABA receptor gene unc-49. One acetylcholine receptor was activated by the nematocide levamisole. This response was eliminated in mutants lacking either the unc-38 or unc-29 genes, which encode alpha and non-alpha acetylcholine receptor subunits, respectively. The second, previously undescribed, acetylcholine receptor was activated by nicotine, desensitized rapidly and was selectively blocked by dihydro-beta-erythroidine, thus explaining the residual motility of unc-38 and unc-29 mutants. By recording spontaneous endogenous currents and selectively eliminating each of these receptors, we demonstrated that all three receptor types function at neuromuscular synapses. (+info)
Quality of life as subjective experience: reframing of perception in patients with colon cancer undergoing radical resection with or without adjuvant chemotherapy. Swiss Group for Clinical Cancer Research (SAKK)
PURPOSE AND BACKGROUND: We examined whether patients with colon cancer undergoing surgery with or without adjuvant chemotherapy change the internal standards on which they base their quality-of-life (QL) estimation, and, if they do so, whether this reframing alters interpretation of QL findings. These questions were addressed within a randomized clinical trial of the Swiss Group for Clinical Cancer Research (SAKK 40/93). PATIENTS AND METHODS: After radical resection of adenocarcinoma of the colon (pT1-4pN > 0M0 and pT3-4pN0M0) and perioperative chemotherapy, patients were randomized to three treatment arms: observation only (A), 5-FU 450 mg/m2 plus Levamisol (B), or 5-FU 600 mg/m2 (C). QL was measured by linear analogue self-assessment indicators. Patients estimated their pre-surgery QL both before surgery and retrospectively thereafter, and their pre-adjuvant QL both at the beginning of randomly assigned chemotherapy or observation and retrospectively about two months later. Thereafter, current QL was assessed. Paired t-tests were used to test the hypotheses of no change. RESULTS: Overall, 187 patients with at least one pair of corresponding questionnaires were analyzed. Patients estimated their pre-surgery QL after surgery significantly lower than before and their pre-adjuvant QL under treatment or observation also lower than at the beginning. In the adjuvant phase, in contradiction to our hypothesis, chemotherapy had almost no impact on these changes attributed to reframing. Conventionally assessed changes indicated an improvement in QL. Patients with treatment C reported less improvement in functional performance than those with B or those under observation (P = 0.04). Patients with treatment B indicated a greater worsening in nausea/vomiting than those with C, whereas patients with observation only showed an improvement (P = 0.0009). After adjustment of current QL scores under treatment or observation to patients' retrospective estimation, the treatment effects were diluted but the overall improvement was substantially amplified in most QL indicators. CONCLUSIONS: Patients with colon cancer substantially reframe their perception in estimating QL both under radical resection and under adjuvant chemotherapy or observation. This effect is an integral part of patients' adaptation to disease and treatment. An understanding of this phenomenon is of particular relevance for patient care. Its role in evaluating QL endpoints in clinical trials needs further investigation. (+info)
Clinical trial to assess the relative efficacy of fluorouracil and leucovorin, fluorouracil and levamisole, and fluorouracil, leucovorin, and levamisole in patients with Dukes' B and C carcinoma of the colon: results from National Surgical Adjuvant Breast and Bowel Project C-04.
PURPOSE: To compare the efficacy of leucovorin-modulated fluorouracil (FU+LV) with that of fluorouracil and levamisole (FU+LEV) or with the combination of FU+LV and levamisole (FU+LV+LEV). PATIENTS AND METHODS: Between July 1989 and December 1990, 2,151 patients with Dukes' B (stage II) and Dukes' C (stage III) carcinoma of the colon were entered onto National Surgical Adjuvant Breast and Bowl Project protocol C-04. Patients were randomly assigned to receive FU+LV (weekly regimen), FU + LEV, or the combination of FU+LV+LEV. The average time on study was 86 months. RESULTS: A pairwise comparison between patients treated with FU+LV or FU+LEV disclosed a prolongation in disease-free survival (DFS) in favor of the FU+LV group (65% v 60%; P =.04); there was a small prolongation in overall survival that was of borderline significance (74% v 70%; P =.07). There was no difference in the pairwise comparison between patients who received FU+LV or FU+LV+LEV for either DFS (65% v 64%; P =.67) or overall survival (74% v 73%; P =.99). There was no interaction between Dukes' stage and the effect of treatment. CONCLUSION: In patients with Dukes' B and C carcinoma of the colon, treatment with FU+LV seems to confer a small DFS advantage and a borderline prolongation in overall survival when compared with treatment with FU+LEV. The addition of LEV to FU+LV does not provide any additional benefit over and above that achieved with FU+LV. These findings support the use of adjuvant FU+LV as an acceptable therapeutic standard in patients with Dukes' B and C carcinoma of the colon. (+info)
Anti-tumour and anti-metastatic activity of 3-(P-Chlorophenyl)-2,3-Dihydro-3-Hydroxythiazolo (3,2-A)-Benzimidazole-2-acetic acid (WY-13,876).
Extensive investigation of 3-(p-chlorophenyl)-2,3-dihydro-3-hydroxythiazolo(3,2-alpha)-benzimidazole-2-aceti c acid (Wy-13,876) in BDF1 mice implanted with Lewis lung tumour has shown that it is an effective anti-tumour and anti-metastatic agent. In vitro examination using HEp-2 human epidermal tumour cells has indicated that Wy-13,876 is not cytotoxic. When mice implanted with Lewis lung tumour and treated with Wy-13,876 are also injected with anti-thymocyte serum, an increase in lung metastases is observed suggesting that thymocyte activity is involved in the drug's mechanism of action. An increase in peripheral T lymphocytes observed in rats 18 h after a single oral dose of Wy-13,876 further supports this possibility. When Wy-13,876 is given to tumour -bearing mice in combination with low, ineffective doses of 5-fluorouracil or cyclophosphamide, further reduction of primary tumour growth is observed. (+info)
In vitro stimulation of murine lymphoid cell cultures by levamisole.
Levamisole has been reported to act as an immunological adjuvant. Experiments reported here on the effect of this agent on a variety of murine lymphoid culture systems were designed to gain an insight into its mechanism of action. We have found levamisole to be a weak mitogen for mouse spleen cells producing a dose related response which peaks at 48 hr in culture. The drug acted to augment the response of spleen cells to sub-optimal concentrations of concanavalin A, but had no unusual effect on the lipopolysaccharide stimulation of B-cell DNA synthesis in vitro. Levamisole was directly stimulatory on enriched T-cell populations and was found to have two actions: (1) to stimulate a subpopulation of T cells and (2) to augment the response of suboptimal mitogen concentrations of concanavalin A. In addition, we have found that murine thymocytes stimulated by concanavalin A were greatly potentiated in the presence of levamisole, but this population of cells could not be stimulated directly by the drug. (+info)
The effect of Levamisole on peripheral blood lymphocyte subpopulations in patients with rheumatoid arthritis and ankylosing spondylitis.
Although Levamisole, an antihelmintic drug, has shown to have some modulatory effect on the immune response in clinical trials and experimental models, its mode of action remains obscure. In a group of fifteen patients with rheumatoid arthritis and ankylosing spondylitis receiving Levamisole on an intermittant regime, simultaneous determinations of the lymphocyte subpopulations were made prior to Levamisole administration and 3 months thereafter. No significant changes were observed either in the absolute or in the relative number of T- and B-cell populations, while a statistically significant reduction was found in the "null" cells. These findings suggest that the immune potentiating effect of Levamisole may at least partially be due to a maturation process of the "null" cells. (+info)
Peripheral blood lymphocyte populations in chronic liver disease.
Mature T lymphocyte concentrations are reduced, null cell concentrations are increased, and Fc receptor bearing (B and K) lymphocyte concentrations are normal, in the peripheral blood of patients with chronic hepatocellular or cholestatic liver disease. Some null cells can be stimulated by either thymosin or levamisole to form rosettes with sheep erythrocytes. These changes are present in viral, alcohol associated and 'autoimmune' liver disease and are therefore probably secondary phenomena relating to liver damage. (+info)