Paullinia cupana Mart var. sorbilis, guaraná, reduces cell proliferation and increases apoptosis of B16/F10 melanoma lung metastases in mice

We showed that guaraná (Paullinia cupana Mart var. sorbilis) had a chemopreventive effect on mouse hepatocarcinogenesis and reduced diethylnitrosamine-induced DNA damage. In the present experiment, we evaluated the effects of guaraná in an experimental metastasis model. Cultured B16/F10 melanoma cells (5 x 10(5) cells/animal) were injected into the tail vein of mice on the 7th day of guaraná treatment (2.0 mg P. cupana/g body weight, per gavage) and the animals were treated with guaraná daily up to 14 days until euthanasia (total treatment time: 21 days). Lung sections were obtained for morphometric analysis, apoptotic bodies were counted to calculate the apoptotic index and proliferating cell nuclear antigen-positive cells were counted to determine the proliferation index. Guaraná-treated (GUA) animals presented a 68.6 percent reduction in tumor burden area compared to control (CO) animals which were not treated with guaraná (CO: 0.84 ± 0.26, N = 6; GUA: 0.27 ± 0.24, N = 6; P = 0.0043), a 57.9 percent reduction in tumor proliferation index (CO: 23.75 ± 20.54, N = 6; GUA: 9.99 ± 3.93, N = 6; P = 0.026) and a 4.85-fold increase in apoptotic index (CO: 66.95 ± 22.95, N = 6; GUA: 324.37 ± 266.74 AB/mm², N = 6; P = 0.0152). In this mouse model, guaraná treatment decreased proliferation and increased apoptosis of tumor cells, consequently reducing the tumor burden area. We are currently investigating the molecular pathways of the effects of guaraná in cultured melanoma cells, regarding principally the cell cycle inhibitors and cyclins.

Absence of peripheral blood mononuclear cells priming in hemodialysis patients

As a consequence of the proinflammatory environment occurring in dialytic patients, cytokine overproduction has been implicated in hemodialysis co-morbidity. However, there are discrepancies among the various studies that have analyzed TNF-alpha synthesis and the presence of peripheral blood mononuclear cell (PBMC) priming in this clinical setting. We measured bioactive cytokine by the L929 cell bioassay, and evaluated PBMC TNF-alpha production by 32 hemodialysis patients (HP) and 51 controls. No difference in TNF-alpha secretion was observed between controls and HP (859 ± 141 vs 697 ± 130 U/10(6) cells). Lipopolysaccharide (5 æg/ml) did not induce any further TNF-alpha release, showing no PBMC priming. Paraformaldehyde-fixed HP PBMC were not cytotoxic to L929 cells, suggesting the absence of membrane-anchored TNF-alpha. Cycloheximide inhibited PBMC cytotoxicity in HP and controls, indicating lack of a PBMC TNF-alpha pool, and dependence on de novo cytokine synthesis. Actinomycin D reduced TNF-alpha production in HP, but had no effect on controls. Therefore, our data imply that TNF-alpha production is an intrinsic activity of normal PBMC and is not altered in HP. Moreover, TNF-alpha is a product of de novo synthesis by PBMC and is not constitutively expressed on HP cell membranes. The effect of actinomycin D suggests a putative tighter control of TNF-alpha mRNA turnover in HP. This increased dependence on TNF-alpha RNA transcription in HP may reflect an adaptive response to hemodialysis stimuli

A priori estimation of accuracy and of the number of wells to be employed in limiting dilution assays

The use of limiting dilution assay (LDA) for assessing the frequency of responders in a cell population is a method extensively used by immunologists. A series of studies addressing the statistical method of choice in an LDA have been published. However, none of these studies has addressed the point of how many wells should be employed in a given assay. The objective of this study was to demonstrate how a researcher can predict the number of wells that should be employed in order to obtain results with a given accuracy, and, therefore, to help in choosing a better experimental design to fulfill one's expectations. We present the rationale underlying the expected relative error computation based on simple binomial distributions. A series of simulated in machina experiments were performed to test the validity of the a priori computation of expected errors, thus confirming the predictions. The step-by-step procedure of the relative error estimation is given. We also discuss the constraints under which an LDA must be performed

Thioglycollate-elicited murine macrophages are cytotoxic to Mycoplasma arginini-infected YAC-1 tumor cells

Macrophages are important components of natural immunity involved in inhibition of tumor growth and destruction of tumor cells. It is known that these cells can be activated for tumoricidal activity by lymphokines and bacterial products. We investigated whether YAC-1 tumor cells infected with Mycoplasma arginini stimulate nitric oxide (NO) release and macrophage cytotoxic activity. Thioglycollate-elicited macrophages from male BALB/c mice were co-cultured for 20 h with YAC-1 tumor cells infected or not with Mycoplasma arginini. The cytotoxic activity was evaluated by MTT assay and nitrite levels were determined with the Griess reagent. Thioglycollate-elicited macrophages co-cultured with noninfected YAC-1 cells showed low cytotoxic activity (34.7 ñ 8.6per cent) and low production of NO (4.7 ñ 3.1 µM NO2-). These macrophages co-cultured with mycoplasma-infected YAC-1 cells showed significantly higher cytotoxic activity (61.4 ñ 9.1 per cent; P=0.05) and higher NO production (48.5 ñ 13 µM NO2-; P=0.05). Addition of L-NAME (10 mM), an inhibitor of NO synthesis, to these co-cultures reduced the cytotoxic activity to 37.4 ñ 2per cent (P=0.05) and NO production to 3 ñ 4 µM NO2- (P=0.05). The present data show that Mycoplasma arginini is able to induce macrophage cytotoxic activity and that this activity is partially mediated by NO.

Superoxide-independent hydrogen peroxide release by activated macrophages

The present data show that freshly explanted BCG-activated mouse peritoneal macrophages release large quantities of hydrogen peroxide upon initial contact with a foreign substratum, without the requirement for other membrane stimuli such as phorbol diesters. The hydrogen peroxide detected under these conditions does not originate from extracellularly released superoxide, since 2 x 10**5 BCG-activated macrophages spontaneously released 1.6 nmol hydrogen peroxide but only 0.2 nmol superoxide. Thus, more than 90% of the hydrogen peroxide detected was not derived from extracellular superoxide dismutation. The dissociation between hydrogen peroxide and superoxide release was further demonstrated in cytochalasin B- or lidocaine-treated cells or in the absence of glucose. Under these conditions, hydrogen peroxide release was markedly inhibited while superoxide release was unaffected. These observations provide evidence that another metabolic pathway is involved in the generation and release of hydrogen peroxide during adherence and spreading of freshly explanted activated macrophages onto a substratum

Murine delayed type hypersensitivity is suppressed by Ascaris suum extract

We studied the suppressive effect of an Ascaris suum extract on delayed-type hypersensitivity (DTH) reactions to ovalbumin (OVA) and to Bacillus Calmette-Guerin (BCG). The ability of mice to develop DTH reactions to both antigens was suppressed when an immunizing dose of the antigen was given subcutaneously together with the Ascaris extract. Partial or complete suppression of the response to OVA was obtained by the use of 400 por 1000 microng of Ascaris extract, respectively. The response to BCG, on the other hand, was totally suppressed by 400 microng of extract